New Japanese Guidelines for the Information of the Prospect of Seismic Activity After Large Earthquakes and Their Applications

2017 ◽  
Vol 12 (6) ◽  
pp. 1109-1116
Author(s):  
Noriko Kamaya ◽  
Kiyoshi Takeda ◽  
Tetsuo Hashimoto ◽  
◽  
Keyword(s):  
Seismic Activity ◽  
Seismic Intensity ◽  
Aftershock Sequence ◽  
Lessons Learned ◽  
Japan Meteorological Agency ◽  
Aftershock Activity ◽  
Research Committee ◽  
New Guidelines ◽  
Large Earthquakes ◽  
Strong Ground

The Kumamoto Prefecture suffered an earthquake of MJMA6.5 on April 14, 2016 at 21:26 (Japan Standard Time). A seismic intensity of 7, on the Japan Meteorological Agency (JMA) seismic intensity scale, was observed, which, by definition, is the maximum possible value. After 18 hours of the earthquake, the JMA issued a prospect for aftershock activity, where the probability of aftershocks with a seismic intensity of 6 Lower (6-) or greater, was 20% within three days following 16:00 JST on April 15, 2016. Ten hours post the issuance of the prospect, at 01:25 on April 16, a larger earthquake of MJMA7.3, with a maximum JMA seismic intensity of 7, occurred in the same region as the MJMA6.5 event, triggering many distant earthquakes. As this seismic occurrence did not follow a mainshock-aftershock sequence, the JMA discontinued the issuance of prospective aftershock activity. With lessons learned from this occurrence sequence, the Earthquake Research Committee of Japan (ERC), including JMA, seismologists and social scientists, have formulated new guidelines for the assessment of successive seismic activity, in order to enhance the understanding of strong ground motions after large earthquakes. The five main points of the guidelines are as follows: (1) alert to a similar strong ground motion, (2) highlighting previous examples of successive large events, (3) consideration of all active source faults, (4) quantitative forecasting of aftershocks a week after the event, and (5) not using the term “aftershock” in information issued by the JMA for disaster prevention. The JMA has commenced the implementation of these new guidelines, effective August 2016.

scholarly journals Spatial distributions of earthquake-induced landslides and hillslope preconditioning in the northwest South Island, New Zealand

2015 ◽  
Vol 3 (4) ◽  
pp. 501-525 ◽  
Author(s):  
R. N. Parker ◽  
G. T. Hancox ◽  
D. N. Petley ◽  
C. I. Massey ◽  
A. L. Densmore ◽  
...  
Keyword(s):  
New Zealand ◽  
Regional Scale ◽  
Aftershock Sequence ◽  
Spatial Distributions ◽  
Damage State ◽  
History Of ◽  
Analysis Of Failures ◽  
Seismic Landslide ◽  
Large Earthquakes ◽  
Strong Ground

Abstract. Current models to explain regional-scale landslide events are not able to account for the possible effects of the legacy of previous earthquakes, which have triggered landslides in the past and are known to drive damage accumulation in brittle hillslope materials. This paper tests the hypothesis that spatial distributions of earthquake-induced landslides are determined by both the conditions at the time of the triggering earthquake (time-independent factors) and the legacy of past events (time-dependent factors). To explore this, we under\\-take an analysis of failures triggered by the 1929 Buller and 1968 Inangahua earthquakes, in the northwest South Island of New Zealand. The spatial extents of landslides triggered by these events were in part coincident. Spatial distributions of earthquake-triggered landslides are determined by a combination of earthquake and local characteristics, which influence the dynamic response of hillslopes. To identify the influence of a legacy from past events, we first use logistic regression to control for the effects of time-independent variables. Through this analysis we find that seismic ground motion, hillslope gradient, lithology, and the effects of topographic amplification caused by ridge- and slope-scale topography exhibit a consistent influence on the spatial distribution of landslides in both earthquakes. We then assess whether variability unexplained by these variables may be attributed to the legacy of past events. Our results suggest that hillslopes in regions that experienced strong ground motions in 1929 were more likely to fail in 1968 than would be expected on the basis of time-independent factors alone. This effect is consistent with our hypothesis that unfailed hillslopes in the 1929 earthquake were weakened by damage accumulated during this earthquake and its associated aftershock sequence, which influenced the behaviour of the landscape in the 1968 earthquake. While our results are tentative, they suggest that the damage legacy of large earthquakes may persist in parts of the landscape for much longer than observed sub-decadal periods of post-seismic landslide activity and sediment evacuation. Consequently, a lack of knowledge of the damage state of hillslopes in a landscape potentially represents an important source of uncertainty when assessing landslide susceptibility. Constraining the damage history of hillslopes, through analysis of historical events, therefore provides a potential means of reducing this uncertainty.

Background Seismicity before and after the 1976 Ms 7.8 Tangshan Earthquake: Is Its Aftershock Sequence Still Continuing?

2020 ◽  
Author(s):  
Yue Liu ◽  
Jiancang Zhuang ◽  
Changsheng Jiang
Keyword(s):  
Aftershock Sequence ◽  
Tangshan Earthquake ◽  
Aftershock Activity ◽  
Background Rate ◽  
Epidemic Type Aftershock Sequence ◽  
Aftershock Sequences ◽  
Background Seismicity ◽  
Before And After ◽  
Large Earthquakes ◽  
Current Stage

Abstract The aftershock zone of the 1976 Ms 7.8 Tangshan, China, earthquake remains seismically active, experiencing moderate events such as the 5 December 2019 Ms 4.5 Fengnan event. It is still debated whether aftershock sequences following large earthquakes in low-seismicity continental regions can persist for several centuries. To understand the current stage of the Tangshan aftershock sequence, we analyze the sequence record and separate background seismicity from the triggering effect using a finite-source epidemic-type aftershock sequence model. Our results show that the background rate notably decreases after the mainshock. The estimated probability that the most recent 5 December 2019 Ms 4.5 Fengnan District, Tangshan, earthquake is a background event is 50.6%. This indicates that the contemporary seismicity in the Tangshan aftershock zone can be characterized as a transition from aftershock activity to background seismicity. Although the aftershock sequence is still active in the Tangshan region, it is overridden by background seismicity.

Emergency Response to Sediment-Related Disasters Caused by Large Earthquakes in Japan - the Case of the Iwate-Miyagi Nairiku Earthquake in 2008 -

2010 ◽  
Vol 5 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Shin’ya Katsura ◽  
◽  
Yoko Tomita ◽  
Nobutomo Osanai ◽  
Chiaki Inaba ◽  
...  
Keyword(s):  
Emergency Response ◽  
Slope Failure ◽  
Central Government ◽  
Seismic Intensity ◽  
Japan Meteorological Agency ◽  
Mountainous Area ◽  
Slope Failures ◽  
Landslide Dams ◽  
Large Earthquakes ◽  
Emergency Measures

Learning the lessons to be taught by large earthquakes of the past is one key to solving the problems of sediment-related disasters of the future, including slope failures, deep-seated landslides, and landslide dam (natural barriers formed by landslides). Our case subject is the Iwate-Miyagi Nairiku Earthquake in 2008 and the emergency response to disasters of Japan’s central government and other organizations. The earthquake occurred on 14th June 2008 and had a JMA (Japan Meteorological Agency) magnitude of 7.2 and a maximum seismic intensity of 6 upper on the JMA seismic intensity scale. The hypocenter in a mountainous area underlain by thick volcanic ejecta triggered over 3,000 slope failures, deep-seated landslides, and debris flows. The earthquake created 15 landslide dams which were expected to cause serious damage downstream if dams collapsed. Emergency measures taken included channel excavation and pumping of landslide dams. Moreover, emergency checking of potential danger sites immediately after the earthquake found 20 sites requiring emergency measures. The relationship between seismic intensity and sites of slope failure and deep-seated landslide showed that seismic intensity exceeding 5 upper caused such disasters and required emergency checking.

scholarly journals A statistical feature of anomalous seismic activity prior to large shallow earthquakes in Japan revealed by the pattern informatics method

2014 ◽  
Vol 14 (4) ◽  
pp. 849-859 ◽  
Author(s):  
M. Kawamura ◽  
Y.-H. Wu ◽  
T. Kudo ◽  
C.-c. Chen
Keyword(s):  
Seismic Activity ◽  
Characteristic Time ◽  
Statistical Test ◽  
Time Span ◽  
Japan Meteorological Agency ◽  
Pi Method ◽  
Pattern Informatics ◽  
Shallow Earthquakes ◽  
The Relationship ◽  
Large Earthquakes

Abstract. To reveal the preparatory processes of large inland earthquakes, we systematically applied the pattern informatics (PI) method to earthquake data of Japan. We focused on 12 large earthquakes with magnitudes greater than M = 6.4 (based on the magnitude scale of the Japan Meteorological Agency) that occurred at depths shallower than 30 km between 2000 and 2010. We examined the relationship between the spatiotemporal locations of these large shallow earthquakes and the locations of PI hotspots, which correspond to grid cells of anomalous seismic activity during a designated time span. Based on a statistical test conducted using Molchan's error diagram, we investigated whether precursory anomalous seismic activity occurred in association with these large earthquakes and, if so, studied the characteristic time spans of such activity. Our results indicate that Japanese inland earthquakes with M ≥ 6.4 are typically preceded by anomalous seismic activity in timescales of 8–10 years.

Seismic Intensity Estimation through Questionnaire Survey and Collapse Rates of Various Building Types in the 2003 Bam, Iran, Earthquake

2007 ◽  
Vol 23 (4) ◽  
pp. 841-865 ◽  
Author(s):  
Tetsuo Tobita ◽  
Masakatsu Miyajima ◽  
Abdolhossein Fallahi ◽  
Reza Alaghebandian ◽  
Mohanmad Reza Ghayamghamian
Keyword(s):  
Questionnaire Survey ◽  
Spectral Ratio ◽  
Peak Frequency ◽  
Seismic Intensity ◽  
Observation Point ◽  
Japan Meteorological Agency ◽  
Epicentral Area ◽  
Reinforced Masonry ◽  
Large Earthquakes ◽  
Microtremor Measurements

Seismic intensity in the epicentral area of the 2003 Bam, Iran earthquake is estimated using a questionnaire survey conducted two months after the earthquake. The estimated average seismic intensity on the Japan Meteorological Agency (JMA) scale is 6.1 (VIII to IX in the MMI scale). The peak frequency of the horizontal-to-vertical spectral ratio derived from microtremor measurements conducted during reconnaissance is also compared with the seismic intensity. Collapse rates for various structure types, such as adobe, unreinforced/reinforced masonry, steel-frame, and reinforced concrete, are obtained by counting the number of demolished buildings within an area of about 50-m radius around an observation point. Results show large differences in collapse rates between unreinforced and reinforced masonry, and suggest the upper limit of seismic intensity that unreinforced masonry can sustain. This fact can be utilized for an initial damage assessment within affected areas after large earthquakes.

A semi-empirical method for simulating strong ground motions based on variable-slip rupture models for large earthquakes

1999 ◽  
Vol 89 (1) ◽  
pp. 36-53
Author(s):  
Kazuo Dan ◽  
Toshiaki Sato
Keyword(s):  
Slip Velocity ◽  
Ground Motions ◽  
Seismic Intensity ◽  
Empirical Method ◽  
Source Inversion ◽  
Tokyo Metropolitan Area ◽  
Rupture Model ◽  
Semi Empirical ◽  
Large Earthquakes ◽  
Strong Ground

Abstract Variable-slip rupture models for large earthquakes, obtained by the source inversion of long-period (>4 sec) seismic waves, are taken into account in a semi-empirical method for simulating broadband (< about 10 sec) strong ground motions. The high-frequency (>0.25 Hz) source spectrum of the (p, q)th subfault is inferred by the θ−2 mode with two circular corner frequencies. The first is ωDpq = Vpq/Dpq, due to the temporal integration of the slip-velocity time function, where Vpq is the maximum slip velocity and Dpq is the final slip. The other is ωSpq = 2βpq/λpq, due to the spacial integration of the slip-velocity time function on the subfault, where βpq is the S-wave velocity of the medium and λpq is the equivalent radius of the subfault. Here, Vpq, Dpq, βpq, and λpq are specified by the long-period source-inversion results. First, we describe this new method by applying it to the variable-slip rupture model for the 1985 Michoacan, Mexico, earthquake of MS 8.1 obtained by Mendoza and Hartzell (1989). The simulated accelerations and velocities at CAL (Caleta de Campos) and VIL (La Villita), both located above the ruptured zone, are in good agreement with the observed ones. Next, the method is applied to the variable-slip rupture model for the 1923 Kanto, Japan, earthquake of MS 8.2 obtained by Wald and Somerville (1995). This earthquake is one of the most important earthquakes for the mitigation of earthquake disaster in the Tokyo metropolitan area; unfortunately, strong-motion records for this earthquake were off-scaled in the region of strong shaking and significant damage. The pseudo-velocity response spectrum of the simulated acceleration of TOK (Tokyo JMA) averages 60 cm/sec in the period range of 0.5 to 10 sec and is consistent with that of the Kanto earthquake record observed at HNG (Hongo, Tokyo), whose off-scaled parts were restored as well as possible by Yokota et al. (1989). The instrumental JMA seismic intensities (JMA, 1996) of the simulated accelerations at TOK and YOK (Yokohama JMA) are consistent with the observed JMA seismic intensity 6 (JMA, 1983). The instrumental JMA seismic intensity of the simulated accelerations at KNS (soil site in Odawara) is also consistent with the JMA seismic intensity 7, estimated from the ratio of collapsed houses (Mononobe, 1925). The simulated broadband (0.1 to 10 sec) motions will be useful in the mitigation of earthquake disaster in the Tokyo metropolitan area.

The U.S. Geological Survey’s Rapid Seismic Array Deployment for the 2019 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 91 (4) ◽  
pp. 1952-1960 ◽  
Author(s):  
Elizabeth S. Cochran ◽  
Emily Wolin ◽  
Daniel E. McNamara ◽  
Alan Yong ◽  
David Wilson ◽  
...  
Keyword(s):  
Fault Zone ◽  
Near Field ◽  
Aftershock Sequence ◽  
Rupture Directivity ◽  
Field Recordings ◽  
Stress Drops ◽  
The City ◽  
Large Earthquakes ◽  
The U.S ◽  
Strong Ground

Abstract Rapid seismic deployments following large earthquakes capture ephemeral near-field recordings of aftershocks and ambient noise that can provide valuable data for seismological studies. The U.S. Geological Survey installed 19 temporary seismic stations following the 4 July 2019 Mw 6.4 and 6 July 2019 (UTC) Mw 7.1 earthquakes near the city of Ridgecrest, California. The stations record the aftershock sequence beginning two days after the mainshock and are expected to remain in the field through approximately January 2020. The deployment augments the permanent seismic network in the area to improve azimuthal coverage and provide additional near-field observations. This article summarizes the motivation and goals of the deployment; details of station installation, instrumentation, and configurations; and initial data quality and observations from the network. We expect these data to be useful for a range of studies including detailing near-field variability in strong ground motions, determining stress drops and rupture directivity of small events, imaging the fault zone, documenting the evolution of crustal properties within and outside of the fault zone, and others.

scholarly journals Characteristics of seismic activity before and after the 2018 M6.7 Hokkaido Eastern Iburi earthquake

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Takao Kumazawa ◽  
Yosihiko Ogata ◽  
Hiroshi Tsuruoka
Keyword(s):  
Seismic Activity ◽  
Main Shock ◽  
Aftershock Sequence ◽  
Aftershock Activity ◽  
Background Rate ◽  
Etas Model ◽  
Epidemic Type Aftershock Sequence ◽  
Aftershock Sequences ◽  
Before And After ◽  
Largest Aftershock

AbstractWe applied the epidemic type aftershock sequence (ETAS) model, the two-stage ETAS model and the non-stationary ETAS model to investigate the detailed features of the series of earthquake occurrences before and after the M6.7 Hokkaido Eastern Iburi earthquake on 6 September 2018, based on earthquake data from October 1997. First, after the 2003 M8.0 Tokachi-Oki earthquake, seismic activity in the Eastern Iburi region reduced relative to the ETAS model. During this period, the depth ranges of the seismicity were migrating towards shallow depths, where a swarm cluster, including a M5.1 earthquake, finally occurred in the deepest part of the range. This swarm activity was well described by the non-stationary ETAS model until the M6.7 main shock. The aftershocks of the M6.7 earthquake obeyed the ETAS model until the M5.8 largest aftershock, except for a period of several days when small, swarm-like activity was found at the southern end of the aftershock region. However, when we focus on the medium and larger aftershocks, we observed quiescence relative to the ETAS model from 8.6 days after the main shock until the M5.8 largest aftershock. For micro-earthquakes, we further studied the separated aftershock sequences in the naturally divided aftershock volumes. We found that the temporal changes in the background rate and triggering coefficient (aftershock productivity) in respective sub-volumes were in contrast with each other. In particular, relative quiescence was seen in the northern deep zones that includes the M5.8 largest aftershock. Furthermore, changes in the b-values of the whole aftershock activity showed an increasing trend with respect to the logarithm of elapsed time during the entire aftershock period, which is ultimately explained by the spatially different characteristics of the aftershocks.

A fault model for the Nahanni earthquakes from aftershock studies

1990 ◽  
Vol 80 (6A) ◽  
pp. 1553-1570 ◽  
Author(s):  
R. B. Horner ◽  
R. J. Wetmiller ◽  
M. Lamontagne ◽  
M. Plouffe
Keyword(s):  
Stress Drop ◽  
Main Shock ◽  
Fault Zones ◽  
Aftershock Sequence ◽  
Aftershock Activity ◽  
Thrust Faulting ◽  
Rupture Plane ◽  
To Come ◽  
Activity Mechanism ◽  
Secondary Fault

Abstract Relative locations of 323 large aftershocks (M 3.0 or greater) in the period from 5 October 1985 to 25 March 1988 show that the Ms 6.6 event on 5 October 1985 initiated at 62.208°N, 124.217°W, about 2.5 km northeast of the Ms 6.9 main shock on 23 December 1985. The overall aftershock distribution suggests the October rupture was primarily a west-dipping, low-angle thrust. In subsequent aftershock activity, the main rupture plane was marked by a distinct quiescent area of about 200 km2 that persisted until the 23 December event. Most of the stress drop and slip occurred in this area. Following the 23 December rupture, a similar sized quiescent zone was also observed; however, it was only evident during the first 24 hr of the aftershock sequence, and the area was about 50 per cent too small to yield the overall stress drop. The additional area appeared to come from secondary rupture zones that developed coincident with the main shock rupture. Precise locations of 182 small (M 3.0 or less) aftershocks recorded during a third field survey from 12 to 21 September 1986 indicated at least one and probably three high-angle faults. Composite mechanism solutions showed thrust faulting except in a region directly south of the main shock rupture areas where there is a bend in one of the secondary fault zones and a concentration of aftershock activity. Mechanism solutions calculated for five of the largest aftershocks in the same region also indicated a similar variability. Development of secondary fault zones explained the increased complexity of the December event and may also provide an explanation for the vertical peak acceleration exceeding 2 g that was recorded about 10 sec after the December rupture initiated.

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