The Largest Expected Earthquake Magnitudes in Japan: The Statistical Perspective (original) (raw)

The Maximum Earthquake Magnitude in a Time Horizon: Theory and Case Studies

Bulletin of the Seismological Society of America, 2013

We show how the maximum magnitude within a pre-defined future time horizon may be estimated from an earthquake catalog within the context of Gutenberg-Richter statistics. The aim is to carry out a rigorous uncertainty assessment and calculate precise confidence intervals based on an imposed level of confidence α. In detail, we present a model for the estimation of the maximum magnitude to occur in a time interval T f in the future, given a complete earthquake catalog for a time period T in the past and, if available, paleoseismic events. For this goal, we solely assume that earthquakes follow a stationary Poisson process in time with unknown productivity Λ and obey the Gutenberg-Richter law in magnitude domain with unknown b value. The random variables Λ and b are estimated by means of Bayes' theorem with non-informative prior distributions. Results based on synthetic catalogs and on retrospective calculations of historic catalogs from the highly active area of Japan and the low-seismicity, but high-risk region Lower Rhine Embayment in Germany indicate that the estimated magnitudes are close to the true values. Finally, we discuss whether the techniques can be extended in order to meet the safety requirements for critical facilities like nuclear power plants. For this aim, the maximum magnitude for all times has to be considered. In agreement with earlier work, we find that this parameter is not a useful quantity from the viewpoint of statistical inference.

An Application of the Time- and Magnitude-Predictable Model for the Long-Term Prediction of Strong Shallow Earthquakes in the Japan Area

The country of Japan and its surrounding area has been divided into 12 seismogenic sources on the basis of certain seismotectonic and geomorphological criteria. In each of these sources, interevent times between successive mainshocks with magnitudes equal to or larger than certain cutoff magnitudes were considered. These interevent times as well as the magnitudes of the mainshocks have been used to determine the following relations: log/', = 0.30 M~n + 0.19 Mp - 0.18 logM0 + 2.41, Mf =- 0.88 Mmi n - 0.25 Mp + 0.46 log/~/0 - 9.06 where Tt is the interevent time measured in years, Mmin is the surface-wave magnitude of the smallest mainshock considered, Mp is the magnitude of the preceding mainshock, Mf is the magnitude of the following mainshock, and M0 is the yearly released seismic moment in each source. On the basis of these two relations, and taking into account the time of occurrence and the magnitude of the last mainshock in each source, time-dependent conditional probabilities for the occurrence of the next large (Ms --- 7.5) shallow mainshocks in the 12 seismogenic sources during the next 10 yrs (1993 to 2002) and the magnitudes of the expected mainshocks are determined. For seismogenic sources 5 (Fukushima), 9 (western Honshu), 7 (southern Hokkaido), 1 (Ryukyu islands), and 12 (Okushiri island), relatively high probabilities (Pl0 ---- 0.5) were assigned. It is of interest to note that in seismogenic source 12 (Okushiri), for which an expected magnitude of 7.5 was calculated, an earthquake with a magnitude of 7.6 (National Earthquake Information Center) occurred on 12 July 1993.

Large-scale short-term seismicity activation prior to the strongest earthquakes of Japan and the Kurile Islands

Izvestiya, Atmospheric and Oceanic Physics, 2011

The Reverse Tracing of Precursors (RTP) algorithm for the prediction of strong earthquakes has become known owing to the successful predictions of the Tokati Oki earthquake near Hokkaido Island and the San Simeon earthquake of California in 2003, as well as to other well documented predictions found on the Internet, some of which also proved to be successful. The RTP predictions with the use of the Japan Mete orological Agency (JMA) data for the zone from Honshu Island to the Middle Kurile Islands deserve special attention. None of the five predictions starting in the middle of 2003, including the last one formulated for the region where the catastrophic earthquake of March 11, 2011, with a magnitude of M = 9 occurred, was a false alarm. One distinctive feature of predictions for this region is the enormous size (about 1000 km) of alarm regions. At the same time, the relatively short alarm interval makes it possible to record a real number of earthquakes with a magnitude of 7.2 and higher during alarm periods, which is about five times larger than on average over the equivalent period, i.e., to reach a probability gain of about five.

Forecasting Probabilistic Seismic Shaking for Greater Tokyo from 400 Years of Intensity Observations

Earthquake Spectra, 2007

The long recorded history of earthquakes in Japan affords an opportunity to forecast seismic shaking exclusively from past shaking. We calculate the time-averaged (Poisson) probability of severe shaking by using more than 10,000 intensity observations recorded since AD 1600 in a 350 km-wide box centered on Tokyo. Unlike other hazard-assessment methods, source and site effects are included without modeling, and we do not need to know the size or location of any earthquake nor the location and slip rate of any fault. The two key assumptions are that the slope of the observed frequency-intensity relation at every site is the same, and that the 400-year record is long enough to encompass the full range of seismic behavior. Tests we conduct here suggest that both assumptions are sound. The resulting 30-year probability of IJMA≥6 shaking (∼ PGA≥0.4 g or MMI≥ IX) is 30%–40% in Tokyo, Kawasaki, and Yokohama, and 10%–15% in Chiba and Tsukuba. This result means that there is a 30% chance that...

Verification of our previous definition of preferred earthquake nucleation areas in Kanto-Tokai, Japan

Tectonophysics, 2006

We have proposed that points of future initiation of rupture may be mapped, based on minima in local recurrence times, which are equivalent to local maxima in the probability for main shocks to occur. These minima are often controlled by anomalously low b-values (logN = a À bM). Of the Kanto-Tokai area, approximately 12% showed anomalously short recurrence times and was proposed as asperities, based on seismicity up to 1999. During the period 1999-2003.5, about 75% of the earthquakes with M z 3.5 fell into the asperities, earlier defined (for example 19 out of 23 M z 3.8 events). The probability for this to occur by chance is approximately 2 10 À 14 . This supports our idea that the most likely volumes to produce main shocks may be mapped by minima in local recurrence times. D

Spatiotemporal variations of seismicity before major earthquakes in the Japanese area and their relation with the epicentral locations

Proceedings of the National Academy of Sciences of the United States of America, 2015

Using the Japan Meteorological Agency earthquake catalog, we investigate the seismicity variations before major earthquakes in the Japanese region. We apply natural time, the new time frame, for calculating the fluctuations, termed β, of a certain parameter of seismicity, termed κ1. In an earlier study, we found that β calculated for the entire Japanese region showed a minimum a few months before the shallow major earthquakes (magnitude larger than 7.6) that occurred in the region during the period from 1 January 1984 to 11 March 2011. In this study, by dividing the Japanese region into small areas, we carry out the β calculation on them. It was found that some small areas show β minimum almost simultaneously with the large area and such small areas clustered within a few hundred kilometers from the actual epicenter of the related main shocks. These results suggest that the present approach may help estimation of the epicentral location of forthcoming major earthquakes.

Past, current and future of Japanese national program for earthquake prediction research

Earth, Planets and Space, 2004

The Japanese national earthquake prediction program started in 1962 with a blue print for the scope and direction of research to follow. Substantial time and efforts were subsequently devoted to the construction of new observation networks and the study on the earthquake generation mechanisms. An important result has been the recognition of the great difficulty in identifying creditable precursors due to a diversity of earthquake generation process. In recent years, a new age of near real time observations of Earth's crustal processes by dense arrays of seismic and the GPS (Global Positioning System) stations has arrived. The results of the real time monitoring may lead to a new approach in the earthquake prediction research, i.e., the quantitative forecasting of the crustal activities. The new national program, which inherits its essential observational network from all the previous programs, emphasizes the importance of modeling as well as monitoring for a sound scientific development of earthquake prediction research.

The 2010-2014.3 global earthquake rate increase

In light of a heightened global earthquake rate during the first quarter of 2014 and recent studies concluding that large earthquakes affect global seismicity for extended periods, we revisit the question whether the temporal distribution of global earthquakes shows clustering beyond that expected from a time-independent Poisson process. We examine a broad window from 1979 to 2014.3 for M ≥ 7.0 shocks, and a narrow window for M ≥ 5.0 seismicity since 2010 that has higher than average rates. We test whether a Poisson process can be falsified at 95% confidence to assess the degree of dependent clustering in the catalogs. If aftershocks within at least one rupture length from main shocks/foreshocks are filtered, then we find no evidence of global scale M ≥ 5.2-5.6 (depending on parameters) clustering since 2010 that demands a physical explanation. There is evidence for interdependence below this threshold that could be a consequence of catalog completeness or a physical process.

Advance short-term prediction of the large Tokachi-oki earthquake, September 25, 2003, M = 8.1 A case history

Earth, Planets and Space, 2004

Tokachi-oki earthquake in northern Japan, September 25, 2003, magnitude 8.1, was predicted six months in advance by a short-term earthquake precursor "chain" that reflects an increase of the correlation range among small earthquakes. This prediction is part of the ongoing test of a new short-term prediction method; the test covers territories of Japan, California, and Eastern Mediterranean. Qualitatively, precursory chain is a dense sequence of small earthquakes that had quickly extended over a long distance. A strong earthquake is expected within nine months after such chain is formed, in its formally defined vicinity. Chains are analyzed in conjunction with intermediate-term precursors, emerging with characteristic lead time of years. Methodology of prediction is named "Reverse Tracing of Precursors" (RTP), since precursors are considered in the reverse order of their appearance. That allows detecting short-term precursors not detectable with direct order of analysis. RTP was tested retrospectively for California, Japan, and Eastern Mediterranean, where 22 more strong earthquakes occurred during the time considered. The concept underlying RTP is interaction of lithosphere dynamics on different temporal scales. The described results enhance our fundamental understanding of lithosphere dynamics and, on the practical side, our capability for earthquakes preparedness.