Prediction of a Second Large Earthquake Based on Aftershock Sequence

2013 ◽  
pp. 27-36 ◽  
Author(s):  
I. A. Vorobyeva ◽  
T. A. Levshina
Keyword(s):  
Large Earthquake ◽  
Aftershock Sequence

The Ceres, South Africa, earthquake of September 29, 1969

1971 ◽  
Vol 61 (4) ◽  
pp. 851-859 ◽  
Author(s):  
R. W. E. Green ◽  
S. Bloch
Keyword(s):  
South Africa ◽  
Fault Plane ◽  
Large Earthquake ◽  
Aftershock Sequence ◽  
Fault System ◽  
Vertical Fault ◽  
Seismic Recording ◽  
The Republic ◽  
Aftershock Region ◽  
Considerable Damage

abstract Aftershocks following the Ceres earthquake of September 29, 1969, (Magnitude 6.3) were monitored using a number of portable seismic recording stations. Earthquakes of this magnitude are rare in South Africa. The event occurred in a relatively densely-populated part of the Republic, and resulted in nine deaths and considerable damage. Accurate locations of some 125 aftershocks delineate a linear, almost vertical fault plane. The volume of the aftershock region is 3 × 9 × 20 km3 with the depth of the aftershocks varying from surface to 9 km. Aftershocks following the September event had almost ceased when another large earthquake (Magnitude 5.7) occurred on April 14, 1970. Following this event, the frequency and magnitude of aftershocks increased, and they were located on a limited portion of the same fault system delineated by the September 29th aftershocks. Previously-mapped faults do not correlate simply with the fault zone indicated by the aftershock sequence.

Real-time discrimination of earthquake foreshocks and aftershocks

2020 ◽  
Author(s):  
Laura Gulia ◽  
Stefan Wiemer
Keyword(s):  
Real Time ◽  
Large Earthquake ◽  
B Value ◽  
Aftershock Sequence ◽  
Main Question ◽  
Traffic Light ◽  
Background Value ◽  
The North ◽  
The Hours ◽  
Average Size

<p>Immediately after a large earthquake, the main question asked by the public and decision-makers is whether it was the mainshock or a foreshock to an even stronger event yet to come. So far, scientists can only offer empirical evidence from statistical compilations of past sequences, arguing that normally the aftershock sequence will decay gradually whereas the occurrence of a forthcoming larger event has a probability of a few per cent.</p><p>We analyse the average size distribution of aftershocks of the 2016 Amatrice–Norcia (Italy) and Kumamoto (Japan) earthquake sequences and we suggest that in many cases it may be possible to discriminate whether an ongoing sequence represents a decaying aftershock sequence or foreshocks to an upcoming large event.</p><p>We propose a simple traffic light classification (FTLS, Foreshock Traffic Light System) to assess in real time the level of concern about a subsequent larger event and test it against 58 sequences, achieving a classification accuracy of 95 per cent.</p><p>We finally test, in near-real-time, the performance of the FTLS to the 2019 Ridgecrest sequence, California: a Mw6.4 followed, about 2 days later, by a Mw7.1. We find that in the hours after the first Ridgecrest event (Mw 6.4, the b-value drops by 23% on average, when compared to the background value, resulting in a ‘red’ foreshock traffic light.</p><p>Mapping in space the changes in b, we identify an area to the north of the rupture plane as the most likely location of a subsequent event. The second mainshock of magnitude 7.1 then indeed occurred in this location and after this event, the b-value increased by 26 percent over the background value, resulting in a green traffic light state.</p>

The prognostic value of foreshocks - a statistical reevaluation

2021 ◽  
Author(s):  
Ester Manganiello ◽  
Marcus Herrmann ◽  
Warner Marzocchi
Keyword(s):  
Physical Process ◽  
Large Earthquake ◽  
Aftershock Sequence ◽  
Earthquake Forecasting ◽  
Earthquake Triggering ◽  
Epidemic Type Aftershock Sequence ◽  
Sequence Selection ◽  
Short Time ◽  
Scientific Questions ◽  
Large Earthquakes

<p>The ability to forecast large earthquakes on short time scales is strongly limited by our understanding of the earthquake nucleation process. Foreshocks represent promising seismic signals that may improve earthquake forecasting as they precede many large earthquakes. However, foreshocks can currently only be identified as such after a large earthquake occurred. This inability is because it remains unclear whether foreshocks represent a different physical process than general seismicity (i.e., mainshocks and aftershocks). Several studies compared foreshock occurrence in real and synthetic catalogs, as simulated with a well-established earthquake triggering/forecasting model called Epidemic-Type Aftershock Sequence (ETAS) that does not discriminate between foreshocks, mainshocks, and aftershocks. Some of these studies show that the spatial distribution of foreshocks encodes information about the subsequent mainshock magnitude and that foreshock activity is significantly higher than predicted by the ETAS model. These findings attribute a unique underlying physical process to foreshocks, making them potentially useful for forecasting large earthquakes. We reinvestigate these scientific questions using high-quality earthquake catalogs and study carefully the influence of subjective parameter choices and catalog artifacts on the results. For instance, we use data from different regions, account for the short-term catalog incompleteness and its spatial variability, and explore different criteria for sequence selection and foreshock definition.</p>

Testing physics and statics based hybrid ETAS models

2021 ◽  
Author(s):  
Shubham Sharma ◽  
Shyam Nandan ◽  
Sebastian Hainzl
Keyword(s):  
Synthetic Data ◽  
Large Earthquake ◽  
Aftershock Sequence ◽  
Additional Stress ◽  
Etas Model ◽  
Epidemic Type Aftershock Sequence ◽  
Stress Changes ◽  
Alternative Approaches ◽  
Large Earthquakes ◽  
Model Approach

<p>Currently, the Epidemic Type Aftershock Sequence (ETAS) model is state-of-the-art for forecasting aftershocks. However, the under-performance of ETAS in forecasting the spatial distribution of aftershocks following a large earthquake make us adopt alternative approaches for the modelling of the spatial ETAS-kernel. Here we develop a hybrid physics and statics based forecasting model. The model uses stress changes, calculated from inverted slip models of large earthquakes, as the basis of the spatial kernel in the ETAS model in order to get more reliable estimates of spatiotemporal distribution of aftershocks. We evaluate six alternative approaches of stress-based ETAS-kernels and rank their performance against the base ETAS model. In all cases, an expectation maximization (EM) algorithm is used to estimate the ETAS parameters. The model approach has been tested on synthetic data to check if the known parameters can be inverted successfully. We apply the proposed method to forecast aftershocks of mainshocks available in SRCMOD database, which includes 192 mainshocks with magnitudes in the range between 4.1 and 9.2 occurred from 1906 to 2020. The probabilistic earthquake forecasts generated by the hybrid model have been tested using established CSEP test metrics and procedures. We show that the additional stress information, provided to estimate the spatial probability distribution, leads to more reliable spatiotemporal ETAS-forecasts of aftershocks as compared to the base ETAS model.</p>

scholarly journals High-resolution 3D earthquake forecasting beneath the greater Tokyo area

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Yosihiko Ogata ◽  
Koich Katsura ◽  
Hiroshi Tsuruoka ◽  
Naoshi Hirata
Keyword(s):  
High Resolution ◽  
Tohoku Earthquake ◽  
Large Earthquake ◽  
Aftershock Sequence ◽  
Earthquake Forecasting ◽  
Plate Boundaries ◽  
3D Space ◽  
Epidemic Type Aftershock Sequence ◽  
Seismicity Rates ◽  
Kanto Region

Abstract We propose an extended 3D space (longitude, latitude, and depth) epidemic-type aftershock sequence (ETAS) model for seismicity forecasts beneath the greater Tokyo area (the Kanto region), which also takes into account the effects induced by the M9 Tohoku-Oki earthquake of 2011. The model is characterized by a number of 3D location-dependent parameters, such as the background seismicity rates, and the productivity rate induced by the Tohoku earthquake. These allow production of high-resolution predictive mappings in zones where hypocenters are densely populated. The optimally inverted 3D spatial images of the characterizing parameters effectively discriminate seismicity features in the crust and near the plate boundaries. The success of the model is demonstrated using short-, intermediate- and long-term probability forecasts of intermediate and large earthquake occurrences beneath the Kanto region.

The Norris Lake Earthquake Swarm of June Through September, 1993; Preliminary Findings

1994 ◽  
Vol 65 (2) ◽  
pp. 167-171 ◽  
Author(s):  
L.T. Long ◽  
A. Kocaoglu ◽  
R. Hawman ◽  
P.J.W. Gore
Keyword(s):  
Earthquake Swarm ◽  
Building Stone ◽  
Aftershock Sequence ◽  
Average Depth ◽  
Induced Earthquakes ◽  
Epicentral Area ◽  
Event Recorder ◽  
Significant Damage ◽  
The 1950S ◽  
Recreational Lake

Abstract During the summer of 1993, the residents in the Norris Lake community, Lithonia, Georgia, were bothered by an incessant swarm of earthquakes. The largest, a magnitude 2.7 on September 23, showed a normal aftershock decay and occurred after the main swarm. Over 10,000 earthquakes have been detected, of which perhaps 500 were felt. The earthquakes began June 8, 1993, with a 5-day swarm. The residents, accustomed to quarry explosions, suspected the quarries of irregular activities. To locate the source of the events, a visual recorder and a digital event recorder were placed in the epicentral area. Ten to 20 events were detected per day for the next three weeks. The swarm then escalated to a peak of over 100 per day by August 15, 1993. Activity following the peak died down to about 10 events per day. The magnitude 2.7 event of September 23 was followed by a normal aftershock sequence. The larger events were felt with intensity V within 2 km of their epicenter, and noticed (intensity II) to a distance of 15 km. Some incidents of cracked wallboard and foundations have been reported, but no significant damage has been documented. Preliminary locations, based on data from digital event recorders, suggest an average depth of 1.0 km. The hypocenters are in the Lithonia gneiss, a massive migmatite resistant to weathering and used locally as a building stone. The epicenters are 1 to 2 km south-southwest of the Norris Lake Community. The cause of the seismicity is not yet known. The earthquakes are characteristic of reservoir-induced earthquakes; however, Norris Lake is a small (96 acres), 2 to 5m deep recreational lake which has existed since the 1950s.

scholarly journals Real-time automatic uncertainty estimation of coseismic single rectangular fault model using GNSS data

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Keitaro Ohno ◽  
Yusaku Ohta ◽  
Satoshi Kawamoto ◽  
Satoshi Abe ◽  
Ryota Hino ◽  
...  
Keyword(s):  
Real Time ◽  
Disaster Response ◽  
Order Approximation ◽  
Nonlinear Problems ◽  
Large Earthquake ◽  
Fault Model ◽  
Deformation Monitoring ◽  
Model Parameters ◽  
The Sea Of Japan ◽  
Plate Interface

AbstractRapid estimation of the coseismic fault model for medium-to-large-sized earthquakes is key for disaster response. To estimate the coseismic fault model for large earthquakes, the Geospatial Information Authority of Japan and Tohoku University have jointly developed a real-time GEONET analysis system for rapid deformation monitoring (REGARD). REGARD can estimate the single rectangular fault model and slip distribution along the assumed plate interface. The single rectangular fault model is useful as a first-order approximation of a medium-to-large earthquake. However, in its estimation, it is difficult to obtain accurate results for model parameters due to the strong effect of initial values. To solve this problem, this study proposes a new method to estimate the coseismic fault model and model uncertainties in real time based on the Bayesian inversion approach using the Markov Chain Monte Carlo (MCMC) method. The MCMC approach is computationally expensive and hyperparameters should be defined in advance via trial and error. The sampling efficiency was improved using a parallel tempering method, and an automatic definition method for hyperparameters was developed for real-time use. The calculation time was within 30 s for 1 × 106 samples using a typical single LINUX server, which can implement real-time analysis, similar to REGARD. The reliability of the developed method was evaluated using data from recent earthquakes (2016 Kumamoto and 2019 Yamagata-Oki earthquakes). Simulations of the earthquakes in the Sea of Japan were also conducted exhaustively. The results showed an advantage over the maximum likelihood approach with a priori information, which has initial value dependence in nonlinear problems. In terms of application to data with a small signal-to-noise ratio, the results suggest the possibility of using several conjugate fault models. There is a tradeoff between the fault area and slip amount, especially for offshore earthquakes, which means that quantification of the uncertainty enables us to evaluate the reliability of the fault model estimation results in real time.

scholarly journals Seismicity, focal mechanism, and stress tensor analysis of the Simav region, western Turkey

2020 ◽  
Vol 12 (1) ◽  
pp. 479-490
Author(s):  
Ahu Kömeç Mutlu
Keyword(s):  
Moment Tensor ◽  
Aftershock Sequence ◽  
Movement Direction ◽  
Normal Faults ◽  
Normal Faulting ◽  
Stress Inversion ◽  
Western Turkey ◽  
Stress Orientations ◽  
Extension Direction ◽  
Inversion Analysis

AbstractThis study focuses on the seismicity and stress inversion analysis of the Simav region in western Turkey. The latest moderate-size earthquake was recorded on May 19, 2011 (Mw 5.9), with a dense aftershock sequence of more than 5,000 earthquakes in 6 months. Between 2004 and 2018, data from earthquake events with magnitudes greater than 0.7 were compiled from 86 seismic stations. The source mechanism of 54 earthquakes with moment magnitudes greater than 3.5 was derived by using a moment tensor inversion. Normal faults with oblique-slip motions are dominant being compatible with the NE-SW extension direction of western Turkey. The regional stress field is assessed from focal mechanisms. Vertically oriented maximum compressional stress (σ1) is consistent with the extensional regime in the region. The σ1 and σ3 stress axes suggest the WNW-ESE compression and the NNE-SSW dilatation. The principal stress orientations support the movement direction of the NE-SW extension consistent with the mainly observed normal faulting motions.

scholarly journals Stress relaxation arrested the mainshock rupture of the 2016 Central Tottori earthquake

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yoshihisa Iio ◽  
Satoshi Matsumoto ◽  
Yusuke Yamashita ◽  
Shin’ichi Sakai ◽  
Kazuhide Tomisaka ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Focal Mechanism ◽  
Large Earthquake ◽  
Static Stress ◽  
Focal Mechanism Solutions ◽  
Large Earthquakes

AbstractAfter a large earthquake, many small earthquakes, called aftershocks, ensue. Additional large earthquakes typically do not occur, despite the fact that the large static stress near the edges of the fault is expected to trigger further large earthquakes at these locations. Here we analyse ~10,000 highly accurate focal mechanism solutions of aftershocks of the 2016 Mw 6.2 Central Tottori earthquake in Japan. We determine the location of the horizontal edges of the mainshock fault relative to the aftershock hypocentres, with an accuracy of approximately 200 m. We find that aftershocks rarely occur near the horizontal edges and extensions of the fault. We propose that the mainshock rupture was arrested within areas characterised by substantial stress relaxation prior to the main earthquake. This stress relaxation along fault edges could explain why mainshocks are rarely followed by further large earthquakes.

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