eEQP-2024:  eEQP-ETRIA TFC-TRAI-2024

 

Earthquake Prediction Research Based on the TRIZ Philosophy

      Toru Nakagawa (Emeritus Professor, Osaka Gakuin University)
      Presented at ETRIA TFC TRAI 2024 Conference, Nov. 6-8, 2024, Cluj-Napoca, Romania

Posted here:   Nov. 26, 2024

Posted:  Nov. 26, 2024

For going to Japanese pages, press buttons. 

Editor's Note  (Toru Nakagawa, Nov. 26, 2024)

This is the paper presented at the ETRIA TFC-TRAI 2024 Conference and officially published by Springer in the Proceedings available at:

© IFIP International Federation for Information Processing 2025
Published by Springer Nature Switzerland AG 2025
D. Cavallucci et al. (Eds.): TFC 2024, IFIP AICT 736, pp. 133–150, 2025.
https://doi.org/10.1007/978-3-031-75923-9_8 

I submitted the paper to the conference on Aug. 12.  I wrote down my thoughts at that time as clearly as possible, especially showing the (general) TRIZ way of thinking in the structure of the paper, partly in response to reviewers' comments.

I was planning to make a trip to Romania, but I had to cancell the trip.  As the world situations in Ukraine and in Palestine were getting severe more and more, I found my health would not allow me to take quick actions in any emergency case.  I submitted my presentation video on October 31st, and the conference organizer kindly played it for me during the session, to my thanks.  If you have any comment or question, please contact me via email.

In this page, I show different types of documents in the following order, for ease of understnding:

Abstract & Keywords          (.html)

Slides with annotation         (.html)            Slides     (.pdf, 10 slides, 2.26 MB)

Video presentation               (.mp4, 16m14s, 17.6 MB)

Paper         (.html)        Paper      (.pdf, 18 pages, 7.1 MB)          Paper published     (.pdf)

(The page in Japanese is not ready yet.)

Table of Contents of the paper:
1. Introduction: 
     1.1  Background:  Earthquakes and Earthquake Prediction Research in Japan;
     1.2  Strategy and Structure of the Present Paper
2. EQ Prediction Research: Problem and the Solution Goal:  
     2.1 EQ Research, EQ Prediction Research, and EQ Disaster Mitigation;
     2.2  Defining the Problem and the Ultimate Goal of Possible Solutions
3. Approaches to EQ Prediction: Criteria and Selection of EQ Precursor Phenomena
     3.1 Requirements for EQ Precursor Phenomena Valid for Short-term EQ Prediction
     3.2 Selection of Promising Precursor Phenomena and Methods
4. Three Promising EQ Precursor Observation Methods
     4.1 Observation of Crustal Strain Using GNSS Satellite Data (M. Kamiyama et al. [3])
    4.2 Observing the Total Electron Content (TEC) of the Ionoshere with GNSS Satellites (K. Heki [4])
    4.3 Observing the Underground Electric Field (Minoru Tsutsui [1])
5. Proposal for a Project to Establish an Imminent EQ Prediction Method based on the Tsutsui Method
6. Concluding Remarks
References


     Earthquake Prediction (EQP) Research Based on the TRIZ Philosophy

Toru Nakagawa   1, 2 [0000-0002-2226-5785]

1 Osaka Gakuin University, Kishibe-Minami, Suita, Osaka, Japan
2 CrePS Institute, 3-1-13 Eirakudai, Kashiwa, Chiba, 277-00086, Japan
nakagawa@ogu.ac.jp

 

Abstract. Suffering earthquake (EQ) disasters, Japan has developed intensive networks of seismographs and achieved probabilistic long-/medium-term forecasting of big EQs.  However, the great disaster EQs of 1995 and 2011were never predicted.  After these two EQs, Seismology Society of Japan and the government decided to avoid investigating the short-term prediction of EQs, considering it impossible.  Earthquake Prediction Society of Japan has been challenging this issue since 2014 and has found a light very recently, especially by observing electromagnetic precursor phenomena.

The present paper first clarifies the requirements for the observation of precursor phenomena to be useful for a future short-term prediction alert system.  Using these criteria, various research presentations are reviewed and three new presentations are found promising.  Especially, M. Tsutsui observed the variation of DC electric field deep underground every second with high S/N ratio.  The electric field generated by piezoelectric effect is transmitted through the earth's crust without being disturbed by noise on the ground.  In the case of EQ (on 2021/5/1, M6.8, 750 km away), the signal showed a drastic (±) variation for 46 min. 1.5 hours before EQ, a sharp spike at the time of EQ, and a drastic variation for 68 min.  8.5 hours after EQ.  The data are excellent, showing the correlation with the EQ and containing much information about the EQ rupture process.   This method is at the stage of single observation site, overcoming various practical difficulties.  The present paper proposes to initiate a collaborative research project within EPSJ with several research groups and observation sites.  The project will certainly step up to prove the correlation with EQs, find the method to predict EQs with 3 factors (where, when, and how large), and establish a system for short-term EQ prediction alert.  The present approach is based on the TRIZ philosophy and experimental science in general and will serve Japan and all over the world.    

Keywords: Earthquake prediction, Short-term/imminent, Observing precursors, TRIZ-guided research strategy

 


  Slides with Annotation                 ==> Slides PDF (10 slides, 2.26 MB)

Hello, everybody !   I'm Toru Nakagawa of Osaka Gakuin University, Japan. 
I am very happy to present my paper in a video, even though I cannot come to Romania mainly because of my health conditions.

My topic today is "Earthquake Prediction Research based on the TRIZ philosophy". 

The EQ in 1995 fell down the main highway from Osaka to Kobe.
At the East Japan Great EQ in 2011,  a tsunami, 10 to 30 meters high, destroyed many cities along the Pacific coast.   Houses were swept by and a big ship was carried up far from the port.

These are the basic motivation of my recent work on the EQ Prediction Research.

This slide shows the relationships among EQ research, EQ Prediction research, Disaster mitigation measures, and People.
All these should work together.  

This slide shows the current status of EQ study, i.e., Conventional Seismology.

These observation studies lead to the study of the physics of EQs, and further to the Long and medium term forecasts of EQs on a probabilistic basis.

However, the short-term and imminent prediction of EQs is regarded impossible in Japan by the Seismological Society and the government, after they failed in foreseeing the two big EQs in 1995 and in 2011.

It is the limitation of the mechanistic approach of the traditional seismology. We should consider various other precursor phenomena, especially electromagnetic ones, just as TRIZ suggests.

In 2014, the EQ Prediction Society of Japan was founded, and I joined it in Feb. 2015.

I expect the stages of EQ Prediction research like this.

At the preparatory stage, we search for various candidates of precursor phenomena of EQs.   Various trials, but we are mostly in the dark.

The first stage is Single site observation of a candidate phenomenon.  We develop the observation method and instrument.
Novel methods by Tsutsui and by Kamiyama are remarkable.

Next is the stage of Multiple sites observation. 
I am proposing a research project for developing the Tsutsui method within our EQ Prediction Society.

At the third stage of Country-wide deployment we establish a method to predict some types of EQs, with the estimation of the 3 factors (where, when, and how large).

At the fourth stage, we Integrate multiple methods for predicting different types of EQs. 

Finally,  we should get understanding and support by academia, society, and government, to start Official operation of warning predicted EQs.

We wish to achieve this in Japan in 20 years.  

 

This slide shows an overview of candidates of EQ precursor phenomena and their observation methods.

It is natural that we first focus on the observation of dynamical phenomena, like these.
However, the timing of the destruction is difficult to predict.
A new method is reported by Kamiyama.

Focusing on Electrical and Electromagnetic phenomena is an important approach.
Various methods of observing Electromagnetic precursor phenomena on the ground have failed because of a lot of noise of nature and artificial origins.
Tsutsui observed the variation of electric field under the ground with high S/N ratio.

 

We now discuss about the Requirements of precursors for Short-term EQ prediction:

The fundamental requirements are:
     The phenomenon X is related with and caused by EQs, and occurs short-time before EQs of various types.
However such requirements can be examined only after extensive observation and analysis.

So we should make our observation method satisfy various requirements step by step:

First, observable/measurable clearly with high S/N ratio.
Second, Observable at multiple sites similarly, and confirming occurrence of EQs just as predicted.
Third, automatic, stable, and continuous measurement, and able to predict the EQs with the three factors (where, when, and how large).
Fourth, the system should integrate various methods for different types of EQs.
Finally, reliable operation of the short-term EQ prediction system.

Our EQ prediction methods and systems should satisfy all these requirements step by step.

 

Now I introduce you the Kamiyama method, as he reported in Dec. 2023.
He uses the precise location data of about 1300 reference points throughout Japan, that are measured and updated every 30 minutes using the GNSS satellites. He uses the triangular mesh to derive the area expansion coefficients for each triangular area.

He reports the case of Hokkaido Iburi East EQ, of magnitude 6.5. Its epicenter is shown here, and more closely here, together with the nearby triangles.

Here, the arear expansion coefficients of the four triangle areas are plotted daily for 13 years from 2011 to 2023. The four areas were initially shrinking slowly at the same rate, then at the EQ on Sept. 6, 2018 two areas suddenly expanded, and after the EQ all the four areas were shrinking slowly again as before.

The lower figure zooms in to the year 2018. The expansion coefficients suddenly showed anomalous variations 3 months before the EQ. Two areas varied positively while two others varied negatively; but, regardless of the direction, the variation patterns were very similar.

From the extent of areas showing such abnormal variations, we can estimate the seismic region and magnitude of the coming EQ.

As for the timing of the coming EQ, he found the cases of 3 years, 2.5 years, and 3 months after the start of abnormal variation, but he has not yet found any further indicators of the timing of EQs.

The Kamiyama Method is now considered most useful and promising for Short-term EQ Prediction.

 

Now I introduce you the excellent work reported by Minoru Tsutsui in Dec. 2022. He observed the DC electric field deep under the ground.

He set his site on a small island at the southern tip of Kii Peninsular to avoid artificial noise. He made a borehole of 150 m deep and set a dipole DC sensor (100 m long) in it. The signal detected passes through a preamplifier, filters, etc. and is stored in a PC every second.

This figure shows the result observed on May 1, 2021. The signal was quiet at first with small noise, and a drastic variation occurred for 46 minutes, then stayed clam. At 10:27, there was a pulse-like signal, followed by another period of calm. Then another drastic variation occurred for 68 min. and became calm.

Later he learned in the official EQ records that there was an EQ exactly at 10:27 with M6.8 off Miyagi (about 750 km away). Accordingly he assigns the first drastic variation as the precursor and the second as the "post-cursor" of the EQ.

This is an epoch-making observation of the EQ precursor, with high S/N, drastic fine structure, 1-sec time resolution, for a significant EQ occurred far away.

The correlation with the EQ is clear; the signals show drastic precursor 1.5 hours before the EQ, and contain rich information about the EQ process, that is not well-known yet.

 

Tsutsui already obtained excellent results, and his method has passed the Stage (1).

At Stage (2), we should initiate a collaborative research project with multiple groups and sites: We try to predict the impending EQs (where, when, how large); We need to raise funding for ourselves.

At Stage (3), our research project should be supported by MEXT. We build a network of about 40 observation sites all over Japan, and we can establish a method for imminent prediction of (some types of) EQs (M > 5.5).

At Stage (4), we integrate various other methods for predicting different types of EQs, and establish a technical system of Short-term/Imminent EQ Prediction.

At Stage (5), Official operation of the warning system of EQ Prediction will start:
Tsutsui method will be the core method for the imminent EQ prediction.

 

Concluding remarks:

EQ prediction research has been in the dark until recently.

● Two novel methods have been developed:
     Kamiyama method will contribute to Short term EQ prediction.
     Tsutsui method is very useful for Imminent EQ prediction

● We should work in a collaborative research project of several groups:

● We work with a country-wide network of observation sites, and establish an EQ prediction method

● We should get the understanding by academia, society, and government

In this manner, Official operation of the warning system of short-term/imminent EQ prediction will start, hopefully in 20 years.

The EQ Prediction research, together with the Disaster Mitigation measures, will certainly contribute to reduce the possible damages caused by many coming EQs in Japan and the world.

Thank you for your attention.

 


  See the Video         ==>    Video (.mp4, 16m14s, 17.6 MB)

 


  Paper        ==>       Paper in PDF (.pdf, 18 pages, 7.1 MB)

 

Published paper

© IFIP International Federation for Information Processing 2025
Published by Springer Nature Switzerland AG 2025
D. Cavallucci et al. (Eds.): TFC 2024, IFIP AICT 736, pp. 133–150, 2025.
https://doi.org/10.1007/978-3-031-75923-9_8  

 

Earthquake Prediction (EQP) Research Based on the TRIZ Philosophy

Toru Nakagawa   1, 2 [0000-0002-2226-5785]

1 Osaka Gakuin University, Kishibe-Minami, Suita, Osaka, Japan
2 CrePS Institute, 3-1-13 Eirakudai, Kashiwa, Chiba, 277-00086, Japan
nakagawa@ogu.ac.jp

 

                       Absract  and Keywords     ==>  See above 

1. Introduction

Recently, I decided to work in the field of earthquake prediction (EQP) research.  My background is not in seismology but in physical chemistry, software engineering, and creative problem solving.  I would like to explain first about the background situation in Japan and why and how I made this decision.

 

1.1  Background:  Earthquakes and Earthquake Prediction Research in Japan

   Japan has frequently suffered disasters caused by large earthquakes (EQs).  In particular, the Great Kanto EQ Disaster (1923) destroyed the Tokyo area (especially the downtown area with fire), the Great Hanshin-Awaji EQ Disaster (1995) attacked the urban structures of Kobe and its surroundings, and the Great East-Japan EQ Disaster (2011) caused a tsunami along the Pacific coast of eastern Japan and led to the serious accident at the Fukushima nuclear power plant.  And now, an EQ ("Nankai Trough EQ") is foreseen to occur in the near future (with 70% probability in the next 30 years), which could cause even greater damage in central and western Japan than in 2011. 

We know that we cannot prevent EQs from occurring, but we, the entire people of Japan and the world, want to reduce the disasters/damage caused by EQs as much as possible.  This desire is, of course, the basis of my decision.

The Seismology Society of Japan (SSJ) was founded in 1880 and developed seismometers and extensive networks of them to observe/analyze EQs and find crustal faults.   A series of five-year research projects on EQ prediction started in 1965 with the support of the Japanese government, and revealed the long-/mid-term forecasting of EQs in various regions with probabilistic possibility.   However, the project never predicted the 1995 EQ (Mw 6.9) nor the 2011 EQ (Mw 9.1).  Faced with this fact, SSJ and the government declared that short-term prediction of EQs is impossible with the current knowledge/technology, and they moved from short-term prediction research to observation and analysis of EQs for more basic understanding. This pessimistic policy is now widely spread in Japan the authorities.

However, many ordinary people wish to have the short-term EQ prediction methods in practice in order to greatly reduce the damage of EQs in the future.  On this background, the Earthquake Prediction Society of Japan (EPSJ) was founded in 2014, and I joined it in Feb. 2015.  EPSJ is a small academic society with about 70 members at present, including 20-30 scientists in seismology besides non-specialists (like me) and amateurs.   One of the main approaches of ESPJ is the observation of electromagnetic phenomena as possible precursors of EQs.  This approach is in good accordance with the TRIZ principle of evolving from mechanical to electromagnetic methods.

I attended the EPSJ conference every year to listen to various presentations and read several books and references.  But none of the methods seemed to me to be effective/reliable until Dec. 2022.

At the EPSJ conference in Dec. 2022 and Dec. 2023, I noticed three novel methods for observing EQ precursors.  In particular, Tsutsui observed drastic fluctuations of DC electric field under the ground from 1.5 hours before to 9.5 hours after an EQ (750 km away, M 6.8) with S/N over 30 and time resolution of 1 sec [1].  Seeing his data, I decided to support the EQ Prediction Research to establish a reliable/practical method for predicting impending EQs [2].

1.2  Strategy and Structure of the Present Paper

The present paper is the result of a typical study of Exploratory Science, especially based on the TRIZ philosophy.  It has the research strategy as follows with the presentation structure shown in ( ):

 

2.  EQ Prediction Research:  Problem and the Solution Goal

2.1  EQ Research, EQ Prediction Research, and EQ Disaster Mitigation

To understand the background of the present study, Figure 1 shows the relationships among EQ research, EQ prediction research, Disaster mitigation measures, and people's desires and preparedness.  EQ research (including EQ prediction research as a part) should work together with Disaster mitigation measures to reduce the disaster/damage that may be caused by EQs.

Fig. 1.  Positioning of EQ Prediction Research [2].   request   information

Fig. 2 shows an overview of the current state of the EQ research, i.e., Seismology. 

Fig. 2.  Seismology:  An Overview of Current State of EQ Research [2]          

    The main activities of current Seismology are Investigation of past EQs, Observation and analysis of EQs with networks of seismographs, Observation of crustal movement by geodetic satellites, and study of the physics of EQs.  They serve to give Long/medium-term forecasting of EQs, in a probabilistic way. e.g., "in region xx an EQ of magnitude about MM may occur with probability 70 % in 30 years".  Such a forecast is useful for planning/implementing long-term measures against possible future EQs.   However, they say "Short-term/imminent prediction of EQs is impossible with current/near-future technology."  Fundamental difficulty stems from the fact that the accumulation of strain energy between a fault takes a very long time (several thousand years to a few years) while the rupture of the fault (i.e., EQ) occurs almost instantaneously (a few seconds to a few minutes).  And they have found no reliable precursors of EQs in their mechanistic perspectives.

    EQ prediction research, on the other hand, aims to invent some reliable methods to give Short-term/imminent prediction of EQs in a deterministic way, such as "in region xx an EQ of magnitude about MM will occur after a short time period TT (with possible reliability of 80%)".  The time period may be progressively shortened, such as weeks, days, hours, and minutes (before an EQ).  This type of EQ prediction is to be announced before EQs, and thus is completely different from the Emergency alarm of EQ occurrence which is announced after an EQ occurrence has been detected.  Thus, our task is much more difficult but useful than the latter.   

2.2  Defining the Problem and the Ultimate Goal of Possible Solutions

    People say: "EQs occur suddenly and cause great disasters/damage.  We want to know shortly in advance where (in a region), when (time period), how big (magnitude range) an EQ will occur, so that we and the whole society should be able to prepare for the impending EQ by protecting ourselves, evacuating, stopping traffic, etc. and to reduce the EQ disasters/damages to considerable extent." 

    So we define our problem as:

"To predict the occurrence of an EQ, specifying where (region), when (time period), and how large (magnitude range), and to announce it publicly in advance of the impending EQ so that the people and the society should be able to protect themselves and to reduce the disasters/damage of the impending EQ."

    seismology of course recognizes this desire/problem but has concluded: "this problem is unsolvable with the present technology/knowledge".  So what are our new keys to solving the problem?

    Our keys are fourfold: 

    --- All these keys are naturally conceived with the philosophy of Exploratory science and strongly supported by the TRIZ philosophy.  

 

   Thus we will set our solution goal as follows:

"(a) To find and observe some precursor phenomena of EQs, (b) to invent a system of methods to predict EQs with reliable estimation of the place (region), time (time period), and magnitude (magnitude range) of the impending EQ in advance, and (c) to announce the EQ prediction warning publicly in advance, so that people and the whole society should be able to prepare themselves against the impend EQ and reduce the EQ disaster/damage significantly."  

   To achieve this solution goal, we allow different choices of approaches to phenomena to observe, methods of estimation, systems of methods, ways of announcement, etc. to create reliable and useful solutions.  However, each of these approaches should pass through the sequential gateways specified above in (a), (b), and (c). 

    For practical reasons, we will describe our solution development in the following five stages, dividing (a) and (b) into two stages:

   It is important that at each intermediate stage we remember the direction of our final goal.  For example, if we choose a phenomenon as a candidate for an EQ precursor, we must consider whether the (possible) method of observing the phenomenon can meet the requirements of later stages.   

 

3.  Approaches to EQ Prediction: Criteria and Selection of EQ Precursor Phenomena

The basic approach to EQ prediction is to identify some characteristic phenomena ("Precursor Phenomena") that occur just before EQs.  Here we first establish the requirements for the precursor phenomena (and the methods that use them), and then select appropriate phenomenon-method pairs for EQ prediction based on the criteria.

3.1  Requirements for EQ Precursor Phenomena Valid for Short-term EQ Prediction

We now consider the criteria/requirements for EQ Precursor Phenomena (and the methods that use them).  It should be noted that as the development of EQ prediction methods, more and more requirements need to be met.  See Figure 3.

Fig. 3.  Precursor requirements for Short-term EQ Prediction [2] with revision

(0) Fundamental requirements: 

  The phenomenon X is related to EQs (correlation); X is caused by EQs (causality); X occurs in some (desirably many) types of EQs; X occurs as a direct effect (or in a short chain of effects) of EQs; X occurs just before (at the pre-rupture stage of) EQs.

     – These are fundamental requirements for an EQ Precursor, but whether a candidate phenomenon X fulfills them or not can be revealed only after systematic observation (experiments) and thorough advanced research on the physical processes of different types of EQs.  This means that EQ prediction research must follow the approach of "Exploratory science", i.e., to think of various candidate phenomena, observe/ measure them carefully, clarify whether they meet the fundamental requirements as EQ precursors, and build a practically useful system of short-term EQ prediction.

 

    We now list the requirements for each stage of solution development:  

Stage (1) Basic Requirements (at an observation site): 

Phenomenon X is clearly observable/measurable (objectively, with high sensitivity, possibly in digital form);  X is free or distinguishable from various natural/artificial noises (by choosing a suitable location, avoiding/reducing noise in the instrument, eliminating/reducing noise with some suitable procedures, etc.); X is measurable with an S/N (signal-to-noise) ratio as high as possible.

    --- These are the basic (and important) level of requirements for observing/measuring the phenomenon X on a single device or site.  To meet these requirements, we need to develop the observation/measurement  methods/devices depending on the phenomenon.  (These requirements  are mostly on the measurement side rather than the phenomenon side.)  The accumulation of observation data at a site will gradually clarify the degree of correlation of X with EQs, i.e., the first Fundamental Requirement on X.

Stage (2) Confirmation Requirements (at multiple observation sites):

    Now multiple sites/devices must be operated in parallel to observe the phenomenon X.  For an EQ, X is observed at multiple sites/devices, simultaneously and similarly;  The closer to the epicenter, the stronger X is observed;  For many EQs, X is observed similarly;  In most cases of observing X, an EQ actually occurred after some short time.

    --- These requirements are important to confirm that the phenomenon X is not a noise but a meaningful signal. (Discriminating signals from noise can be done much more clearly by observing at multiple sites than at one site.)  The accumulation of these data will show that the observing instruments are effective in detecting how far and how large EQs are (i.e., criteria mostly on the instruments). The data will examine/prove the correlation relationships of X with different types of EQs. We should note that X is clearly detected for which types of EQs and how much time in advance of the EQs.  We should also note that X is not detected (or only weakly detected) for some other types of EQs. (This may be the nature of the phenomenon X, depending on the physical processes and types of EQs.  This observation will contribute to a better understanding of EQ processes.)   

Stage (3) Practical Requirements (as a technical method for EQ prediction):

    The phenomenon X is measured in an automatic, stable, and continuous way; Measurement data of X at many sites are collected in a network system to record and analyze them quickly (and later in detail); The measurement data are used to predict a shortly impending EQ with the estimation of where (location region), when (time period), and how large (magnitude), etc.; It is highly desirable for the data of X to show some fine structures reflecting the EQ process. 

    --- These are the requirements at the stage when the phenomenon X is used in a technical system for predicting (some types of) EQs.  Such a technical system should be operated in an automatic, stable, and continuous manner to observe the occurrence of EQs at any place and any time.  A network system is necessary for connect/communication of many observation sites (and their research/operation groups) distributed all over Japan.  Building such a system (including hardware, software, and personnel) will require a large project to complete the stages of proposal, organization, implementation, testing, operation, and prediction.  Thus, the first and second requirements mentioned here are mostly related to the observation system rather than X itself.  The ability to pre-estimate the three factors (i.e., where, when, and how large) of the predicted EQ is critical to the EQ prediction warning.  If any of the three is missing or vague, the EQ prediction is meaningless or useless.  Estimation of the three factors depends mostly on the analytical capability of the software or research team, and partly on the clarity/nature of the observed signals of X (e.g., injection direction of the signal, intensity/time difference at multiple sites, etc.).  If the observed signal of X shows some fine structure (e.g., intensity change with time), there is a possibility to reveal some process/type of the EQ.  We should accumulate the observation and analysis of X for a significant number of cases of EQs to make our prediction and estimation reliable.  

Stage (4) Advanced Requirements (as a technology system for EQ prediction):

    Advantages and limitations of the method of observing X are revealed; Several other methods of observing different phenomena X2, X3, … are also made available (through stages (1)(2)(3) above); By integrating such methods of observing X1, X2, … Xn , a technology system is built to cover desirable time ranges before EQs (e.g., a few months before, days before, …, minutes before) and different types of EQs; The system needs to be tested and refined through many years of operation into a reliable EQ prediction system.   

    --- At this stage, we must be aware of the diversity of EQs (e.g., between plates or within a plate, under the sea or under the land, different EQ processes, etc.) and thus the diversity of precursor generation (e.g., different phenomena at different times, no generation of phenomenon Xi for certain types of EQs, etc.).  We should have multiple observation methods that can be used with different lead times (e.g., 3 months, 1 month, 1 week, 1 day, 3 hours, 1 hour, and 3 minutes before an EQ).  We should also note that the generated signal can sometimes be weakened by barriers, such as the sea and soft land layer.  At this stage, the EQ prediction information should be better managed within the project before the EQ and can be made open to public after the EQ.  The prediction data and the actual events should be carefully analyzed together with various seismological information to examine the Fundamental requirements as EQ precursors (especially on correlation, causality, EQ types, EQ processes, etc.)

Stage (5) Social Requirements (at the stage of official operation of the Short-term/Imminent EQ Prediction Warning):

    After a thorough trial period, the merit/effectiveness/reliability of the Short-term/Imminent EQ Prediction System must be approved by academia, society, and government; The Short-term/Imminent EQ Prediction Warning System is officially operated in public in Japan; The methods and system are to be transferred and applied in many countries around the world.

    ----  This is the ultimate goal of the research project on Short-term/Imminent EQ Prediction methods and systems.  The mechanisms and processes of (various types of) EQs need to be revealed in the academic world in Japan and the world along with the research project.

 

    Most of the above requirements depend on the measurement methods/instruments/ networks/etc. at present and in the future; therefore, we should develop such measurement methods as much as possible and also be aware of their possible limitations.

    Due to the great variety of EQs (e.g., in their geological/crustal structures, components of the crustal layers, depth below ground, etc.), we should expect differences in the mechanisms/processes of EQs, and thus different possible phenomena before/during/after EQs;  therefore, we must be prepared for one phenomenon to be caused by some (not all) types of EQs, for several phenomena to be caused by one type of EQs, and for different types of EQs to have occurred even in a given region in history. 

 

3.2  Selection of Promising Precursor Phenomena and Methods

Using the above requirements as criteria, we should search/select/ develop (multiple) EQ prediction methods that are expected to be feasible/versatile/ reliable/informative/useful for Short-term/Imminent EQ Prediction.  Fig. 4 shows different categories of candidate precursor phenomena and the methods to observe them.

Fig. 4.  Candidate precursor phenomena and the methods of observing them [2]

    The main categories of possible EQ precursor phenomena are mechanical phenomena and electromagnetic phenomena. Note that various other reported or observed phenomena (e.g., abnormal behavior of animals, abnormal shape of clouds, change in underground water levels, increase in radon radiation in the air, etc.) are neglected here because they apparently do not meet the requirements of Stages (1)(2)(3).

3.2.1  Mechanical Phenomena are the Primary Category:

    They include Horizontal/vertical movement of ground points, Pressure/strain at faults in the crust, 'Foreshocks', etc.  Since EQs are generally rupture phenomena caused by the moving pressure between plates/faults, they are primarily related to the mechanical forces/mechanisms/processes and can be observed as mechanical effects. However, the EQ energy at an epicenter is accumulated for a very long time (usually from thousands to tens of years) before the sudden rupture (i.e., an EQ) occurs in a very short time (usually from seconds to minutes).  Therefore, it is very difficult to know in advance when a rupture (EQ) will occur. 

    For example, "foreshocks" do not qualify as EQ precursors.  When an EQ occurs, current seismology cannot judge whether it is a "foreshock" (of a larger "main shock" to come) or not.  To make such a judgment, we need to know whether a plate boundary or faults in the adjacent area can be induced to suddenly release larger energy of accumulated stress in a very short time (e.g., within a week or a month).  Current seismology does not have the ability to judge in advance if and when a larger EQ will be induced, and only after a major EQ (i.e., a "main quake") has occured we can say that we had a "foreshock" beforehand.  

    Similarly, various seismological parameters have been proposed as candidates for EQ precursors, and most of them are useful for long-/medium-term EQ forecasting on a probabilistic basis, but not for short-term EQ prediction. 

Recently, M. Kamiyama et al. [3] demonstrated a method to detect the change in local strain accumulation speed using satellite data.  This method  will be discussed later (Section 4.1).

3.2.2  Electromagnetic Phenomena Are the Second Category.

    The piezoelectric effects in the crust at the epicenter are expected to generate electric fields and then induce magnetic fields, electromagnetic waves, etc.  Such secondary effects are several orders of magnitude smaller in energy than the primary mechanical effects.  However, the large area of the epicenter covers the disadvantage, and the high sensitivity of various electromagnetic observation methods makes them observable in various ways.  The transition from mechanical-based (observation) technology to electromagnetic-based (observation) technology is a typical way of advanced evolution in technology, as is known in TRIZ theory.  We have versatile and sensitive methods for observing/measuring electromagnetic phenomena, which can propagate over long distance in any direction.     

    Observation methods in this broad category can be classified according to the place of detection (on/above the ground, in the atmosphere, in space, under the ground, under the ocean floor, etc.), the target phenomena, and the detection instruments.  The most popular/studied subcategory is, of course, ground-based observations because of their ease of implementation and operation.  Its target phenomena are the variation of the electric field on the ground, the variation of electromagnetic waves of different frequencies (from ULF to VHF) in the air, the variation of the intensity of the MF wave from a distant location and reflected at the ionosphere, etc.  Such phenomena are supposed to be induced by the electromagnetic field in the lithosphere and propagated to the ground surface, atmosphere, and ionosphere, and thus weakened and obscured in these transmission processes.  Implementation of these methods is often straightforward, but natural noise (due to solar radiation, lightning, etc.) as well as artificial noise (due to traffic, living, industrial activities, etc.) are difficult to suppress/discriminate and result in poor, low S/N signals despite high sensitivity of the instruments.  

    Satellite observation of the total electron content (TEC) in the ionosphere (by K. Heki [4]) is a new approach and will be discussed later (Sec. 4.2).

    The observation of the variation of the DC electric field under the ground (150 m deep) (by M. Tsutsui [1]) is highly promising and will be discussed in detail later (Sec. 4.3).

 

4.  Three Promising EQ Precursor Observation Methods 

We now review three EQ precursor observation methods that I consider promising according to the criteria described above.

4.1  Observation of Crustal Strain Using GNSS Satellite Data (M. Kamiyama et al. [3])

    Makoto Kamiyama et al. [3] use the GEONET data provided by the Geospatial Information Authority of Japan (GSI). The precise locations of about 1300 control points all over Japan are continuously determined with the GNSS system and published every 30 minutes.  Kamiyama et al. analyze the daily position data of all points in the triangular network to obtain the maximal sheer strain (γmax) and volumetric strain (dilatation). They demonstrated their analyses for three EQs, representative of the 23 damaging EQs reported by JMA during 5 years from Jul. 2018 to Jul. 2023.  Here we show the largest case, i.e., Hokkaido Iburi East EQ which occurred on 2018/9/6 with MJ 6.5 (See Fig. 5). 

Fig. 5.      Observation of the daily change in crustal stress using GNSS satellite data for one year covering Hokkaido Iburi East EQ (by M. Kamiyama et al. [3]).

    Fig 5a shows the position of the epicenter () in the triangular network. Fig. 5b shows the daily plots (from 2018/1/1 to 2018/12/31) of maximal shear strain at four locations, i.e., the triangle center () and the three triangular points (). These daily plots show an abnormal variation "apparently clear for all" since late May 2018, which  in this case is 3.5 months before the EQ. 

    Summarizing the three cases, the authors find clear abnormal variations with the lead times varying from 3 years to 3 months, with different patterns of variation suggesting stages such as beginning, developing, staying, and ending.  They suggest the possibility of estimating the three EQ factors, i.e., 'where' from the triangular network, 'when' from the time series, and 'what size' from the range of abnormal variation. 

    --- This method provides a new possibility for Short-term Prediction of EQs using geodetic observation, which already covers all areas in Japan. The lead time, from a few years to a few months before the impending EQs, may be useful and will be made clearer by accumulating many cases.  This method has a weak point in observing EQs that occur under the ocean trough. 

4.2  Observing the Total Electron Content (TEC) of the Ionoshere with GNSS Satellites (K. Heki [4])

    Kosuke Heki [4]  developed a method to use the Total Electron Content (TEC) of the ionosphere observed with the GNSS satellites.  The TEC of ionosphere is observed between a pair of a ground station and a GNSS satellite orbiting around.  He shows the case of 2008 Wenchuan EQ in southwest China, which occurred on 2008/5/12 6:28UT. 

Fig. 6.  Observation of the increase in the Total Electron Content (TEC) in the ionosphere (2008 Wenchuan EQ) (by K. Heki [4])

    Fig. 6a shows the locations of the epicenter (, near the upper center of the figure), the ruptured faults (rectangles), the ground station 'meig' (■), and the tracks of several GNSS satellites () (whose ionospheric piercing points (IPP) at the altitude of 200 km from the 'meig' station are projected on the ground) together with the satellite number, direction of travel, and their positions at 5:30, 6:00, and 7:00 UT.  Satellite G09 is found the most advantageous.  Fig. 6b shows the six ground stations near 'meig' and the IPP tracks of G09 as seen from each of them.  Fig. 6c shows the change in Vertical TEC (VTEC) seen with satellite G09 and the six stations during 5.0-7.4 UT.  The background curve is fitted to an  order 2 polynomial with the data excluding the 5.85-7.0 UT portion.  The increase in VTEC is clearly seen starting 37 minutes before the EQ and is estimated to be about 5% of the background VTEC at the time of EQ.  Heki summarizes his results from about 20 cases of large EQs in Fig. 6d.  For EQs with Mw 7.2 – 9.2, the lead time ranges from 10 to 100 minutes while the cumulative anomaly ranges from 0.3 % to 30 %.

    --- The results are clear and consistent by use of careful processing of GNSS satellite data for large EQs. The method observes the change in the total electric content in the ionosphere, which reflects the electric field generated deep in the lithosphere and transmitted through the atmosphere.  This method will be useful for detecting large EQs globally. 

4.3  Observing the Underground Electric Field (Minoru Tsutsui [1])

    Minoru Tsutsui [1] observes the DC electric field deep underground.  Fig. 7a shows his equipment.  He placed the observation site on a small island near the southern tip of the Kii Peninsula, to avoid artificial noise (e.g., residential houses, railways, traffic, etc.) and installed the equipment deep underground to avoid natural noise (e.g., lightning, temperature changes, etc.).  He made a borehole with a diameter of 20 cm and a depth of 150 m to place a linear dipole DC electric sensor with a length 100 m.  A differential amplifier is installed 20 m underground, and a 60 Hz notch filter (to remove power supply frequencies) and a low pass filter are placed on the ground.  The signals are sampled every second and recorded on a PC.  The system achieves a constant noise level of 0.5 μV/m.  In addition, two 5 m long sensors are installed 8 m above the ground to monitor the horizontal electric field  (EW and NS).

Fig. 7.  Observation of the underground DC electric field (by M. Tsutsui [1])

    The equipment operated from April to July 2021 and provided valuable observation data in two forms:  Fig. 7b shows the signals observed on May 1, 2021, with drastic (±) variations of more than 10 μV/m (p-p) for 46 minutes from 08:50, a sharp spark at 10:27, and the second drastic variations for 68 minutes from 19:00.  He later learned that an EQ occurred at the same time (10:27) with M6.8 at a depth of 50 km, off the coast of Miyagi Prefecture (about 750 km away).  He understands the first drastic variation as a precursor to the 10:27 EQ.  But for the signal of the second drastic variation, he cannot find any subsequent EQ (this fact may suggest the observation of a "post-cursor" of the 10:27 EQ).  The horizontal electric field sensors on the ground observed similar fluctuations in both EW and SN directions during the two variation periods mentioned above.  However, the signals were superimposed by gradual fluctuations caused by diurnal changes in the ionospheric electric field.

    Fig. 7c shows the signals observed on May 6, 2021.  The mean electric field rose slowly from 0 to +2 μV/m at 05:25, lasted about 5 hours, dropped to almost 0 and remained there for about 3 hours, then suddenly jumped to +2μV/m at 13:30 and then returned (with some minor fluctuations) to 0 potential in about 6 hours.  He later learned that an EQ occurred at 13:30 with M3.7 at a depth of 50 km in the Kii channel (about 100 km away).  (The horizontal electric field sensors above ground showed gradual noisy fluctuations during the day to hide any information corresponding to the underground data).

    --- We understand that these two forms of observed data are related to the occurrence of EQs as precursors of them and provide certain information about the behavior/process of EQs.  This method is highly valuable for detecting EQs that occur far away under the land or sea, with signals of high S/N and fine structures covering the time range from several hours before to several hours after the EQ.  This method is expected to be useful for predicting imminent EQs and also for studying the physical process of EQs.

 

5.  Proposal for a Project to Establish an Imminent EQ Prediction Method based on the Tsutsui Method

    It is clear that the Tsutsui Method satisfies (1) Basic requirements at the stage of single observation site, and can be expected to technically satisfy (2) Confirmation requirements at the stage of multiple observation sites, and further (3) Practical requirements at the stage of the technical method for EQ prediction.  This result is much better than the other two methods shown in Sections 4.1 and 4.2, and many other methods that have been investigated so far in Japan and in the world.  Therefore, the present paper proposes to initiate a cooperative research project to establish an Imminent EQ Prediction Method based on the Tsutsui Method.

Stage (1) at a Single Observation Site: 

    Tsutsui has already developed his observation equipment and demonstrated excellent observation data, but has various difficulties and problems.  He is an emeritus professor at Kyoto Sangyo University and has been working alone with his personal funding since 2015.  His observation site is far away from Kyoto and needs regular and accidental maintenance from time to time.  His PCs were once hacked and  once crashed, destroying the home-made software and some parts of the observation data.   The observation data are now stored in the site PC without automatic transfer to the home PC.  Only a part of his observation data was published  in Dec. 2022.  The unpublished data must contain rich information of signals in correlation with EQs, possibly with different patterns reflecting different processes of EQs.

Stage (2) with Multiple Observation Sites:

    We should now proceed to the second stage at multiple observation sites by forming a collaborative project of multiple research groups.  The most important task is to get the second and several more research groups who decide to work on this research project seriously by shifting some of their group power.   Discussions within EPSJ about our future research direction will be very helpful to initiate the project.   We should set up several research groups and their observation sites in a distributed manner, such as Sendai, Tsukuba, Chiba, Tokyo, Nagano, Shizuoka, Nagoya, Kyoto, Kochi, etc.  A technical problem for each group is to make an underground borehole in a remote, noise-free location.  We may have an alternative choice of making a deeper borehole in some suburban area for better/easier maintenance.  We also need to build a network system to upload the observation data from all the observation sites and analyze them in a project center and in each group.  Obviously, we need a project organization that decides/guides the research strategy, obtains some funding, and promotes the project to the academia (under the current difficult situation as mentioned in Section 1.1). 

    The research tasks at this stage are shown in Fig. 8 in four phases.

Fig. 8.  Research tasks at Stage (2) with multiple observation sites.

    In Phase 1:  We need to set up multiple observation sites and operate them in parallel.  Review the records of all the sites together and distinguish signals from noise.

    In Phase 2:  Analyze the observation data in relation to the records of EQs published by JMA.   Distinguish the cases of Correlation, Non-correlation, and No-observation, and record the relevant EQs in terms of epicenter, time, magnitude, type, etc.  This will reveal the correlation of (some patterns of) variation of underground DC electric field with (some types of) EQs. 

    In Phase 3:  Using such accumulated data, create a method for estimating the time, place and magnitude of impending EQs. (*Note:  The transmission speed of electric field through the lithosphere is about half the speed of light.  Thus, we can not use the usual method of estimating the location of the epicenter by using the time differences of receiving the EQ signals in the form of P-waves (with the speed of 7 km/s) at 3 (or more) different locations.  We need some additional information, such as the incoming direction of the signals.  Estimation of the magnitude depends on the estimated location.)

     In Phase 4:  Apply the (in-advance) estimation method to cases of significant signals and test how well the prediction agrees (or not) with the EQs that occurred shortly thereafter.  The accumulation of these tests will further refine the prediction method and reveal the reliability and usefulness of this EQ prediction method. 

Stage (3) as a Technical Method for EQ Prediction: 

    When our prediction method successfully passes Stage (2) with multiple sites (Phase 1 through Phase 4), we move on to Stage (3) as a (practical) technical method of EQ Prediction.   As described in Section 3.1(3), we will build several tens of observation sites all over Japan, operate them in an automatic/stable/reliable manner to form a network system, watch for (significant) EQs that may occur at any place at any time, and get ready to predict (possible) impending EQs to alert within the project.  We are sure that the Tsutsui method will certainly develop successfully into such a technical method/system.  It is clear that we should establish a research project based on EPSJ, with many research groups, and officially supported by academia (especially SSJ) and government agencies. 

Stage (4)  as a Complete Technology System for EQ Prediction:  

    At this stage we should integrate a number of complementary EQ Prediction methods.  Tsutsui method uses local observation sites and will be useful to detect the precursor a few hours before the EQs.  Kamiyama method, on the other hand, detects precursors much earlier (a few years to a few months before the EQs) and covers the whole of Japan.  Thus, it will be a nice complementary method to be integrated into the EQ Prediction System.   Heki method detects precursors 100 to 10 minutes before EQs  and can cover the whole globe by using GNSS satellites and many ground stations.  It can be useful for predicting large EQs globally if the prediction algorithm works fast enough.   These two methods, as well as some others that will emerge in the future, will be candidates for integration.  It is ideal to have a versatile set of EQ prediction methods for short-term (e.g., months, weeks, and days before the EQ) and imminent (e.g., hours and minutes before the EQ) , covering different types of EQs.

Stage (5)  Official operation of Short-term/Imminent EQ Prediction Alert: 

    We want to realize the official operation of our Short-term EQ Prediction methods at this stage, hopefully in 20 years or so before the so-called "Nankai Trough Great EQ" hits Japan.  We have to overcome difficult tasks as discussed in Sec. 3.1(5)

 

6.  Concluding Remarks

    Short-term/imminent prediction of EQs has been studied in various ways, but mostly in the dark of chaos, just as the authorities of seismology in Japan stated "Short-term prediction of EQs is impossible with the current technology".  EPSJ has been working on this difficult problem since 2014, and has recently shed light on it with three novel observation methods.

    The present paper finds the keys to build (or innovate) Short-term/Imminent EQ Prediction, i.e., to imagine the rupture (EQ) process accompanying various (electromagnetic besides mechanistic) phenomena and to build solutions step by step.  Thus, we define our problem and our stepwise solution goal, and further describe five stages of solution development (Section 2).  This approach is in good accordance with Exploratory science in general and strongly supported by the TRIZ philosophy.

    Then the present study has clarified the requirements for precursor phenomena and prediction methods at the five stages, and has selected promising studies of phenomenon-method pairs under the criteria of the five-stage requirements (Section 3).

    We review three promising methods, i.e., Kamiyama Method to observe crustal strain, Heki Method to observe  TEC of the ionosphere, and  Tsutsui Method to observe underground electric field.  All three are now at Stage (1) where they observe the target phenomena at a single site (or research group) and try to confirm that the observed phenomenon occurred just before some EQ (Section 4).

    Finding that Tsutsui Method can possibly meet the requirements at all higher stages, the present paper proposes to initiate a collaborative research project on Short-term/Imminent EQ Prediction with Tsutsui Method at the center.  (Section 5).

    We believe that we have just passed the Stage (0) of searching for EQ precursors in the dark and have reached at Stage (1) of working with a clear strategy/vision for building the reliable/versatile technological and social system of Short-term/Imminent Prediction of EQs.  This work will of course serve in Japan and all over the world.

    The present author thanks the two reviewers for clarifying the intention of the paper.

 

References

  1. Minoru Tsutsui, Possibility of Earthquake Prediction by Observing Underground Electric Field, Proceedings of Earthquake Prediction Society of Japan Conference, Dec. 23-24, 2022, Kyoto University & Online, (2022) paper 22-22. (in Japanese)
  2. Toru Nakagawa, On the Direction of Developing Earthquake Prediction Research, Proceedings of Earthquake Prediction Society of Japan Conference, Dec. 22-23, 2023, University of Electro-Communications & Online, (2023) paper 23-12. (in Japanese)
  3. Makoto Kamiyama, Atsushi Mikami, Hideo Koide, Yasuji Sawada, and Hiroshi Akita, Precursor Phenomena of Damaging Earthquakes Observed in the Temporal-Spatial Variations of GNSS Crustal Strain Data,  Proceedings of EPSJ Conference, Dec. 22-23, 2023, University of Electro-Communications & Online, (2023) paper 23-20. (in Japanese)
  4. Kosuke Heki, Ionospheric Changes Immediately Before the 2008 Wenchuan Earthquake,  Proceedings of Earthquake Prediction Society of Japan Conference, Dec. 22-23, 2023, University of Electro-Communications & Online, (2023) paper 23-09.  (in Japanese)

 

 

 

 

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