scholarly journals The aftershock sequence of the Kamchatka earthquake of November 4, 1952

1958 ◽  
Vol 48 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Markus Båth ◽  
Hugo Benioff
Keyword(s):  
Aftershock Sequence ◽  
Stress System ◽  
Time Interval ◽  
Aftershock Activity ◽  
Kamchatka Earthquake ◽  
Strain Release ◽  
Release Curve ◽  
Mohorovičić Discontinuity ◽  
Total Average ◽  
Northern Japan

Abstract Aftershock epicenters of the Kamchatka earthquake of November 4, 1952, are distributed over an area approximately 1,030 kilometers in length by 240 kilometers in width. Assuming that this distribution represents the active strain zone, the total average strain, average elastic energy, and average stress of the rocks before slip were 11.9 × 10−5, 1.35 × 102 ergs/cm.3, and 12.6 kg/cm.2, respectively. The strain-release curve of the sequence has been constructed using observations from Uppsala and Kiruna. The data include more than 400 shocks with magnitudes 6.0 and greater which have occurred up to December, 1956. The curve exhibits three segments each of the form ΣJ1/2 = A + B log t, where J is the energy and t is the time measured from the time of the principal earthquake. The slope B changes abruptly at t = 0.4 days and at t = 195 days, the latter change being particularly pronounced. Moreover, this was accompanied by other evidence suggesting a change in mechanism. The coefficients B have almost the exact ratio of 1 : 2 : 5 in the three intervals 0-0.4, 0.4—195, and after 195 days. The aftershock activity has its highest concentration in the vicinity of the principal earthquake and tapers off toward both ends of the active fault segment. The majority of the aftershocks have clear pP impulses occurring generally 9 to 13 sec. after P, indicating that the foci were in or close to the Mohorovičić discontinuity. The rate of strain accumulation and release for the time interval from 1897 to 1956 for the entire Kamchatka-northern Japan stress system shows a slow decrease with time. Comparison of the rate of the entire system with that of the aftershock sequence leads to an approximate estimate of the possible duration of the sequence.

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.

scholarly journals Statistical physics models for aftershocks and induced seismicity

2018 ◽  
Vol 377 (2136) ◽  
pp. 20170397 ◽  
Author(s):  
Molly Luginbuhl ◽  
John B. Rundle ◽  
Donald L. Turcotte
Keyword(s):  
Induced Seismicity ◽  
Statistical Physics ◽  
Aftershock Sequence ◽  
Induced Earthquakes ◽  
Aftershock Activity ◽  
Gas Field ◽  
Natural Time ◽  
Parkfield Earthquake ◽  
Groningen Gas Field

A standard approach to quantifying the seismic hazard is the relative intensity (RI) method. It is assumed that the rate of seismicity is constant in time and the rate of occurrence of small earthquakes is extrapolated to large earthquakes using Gutenberg–Richter scaling. We introduce nowcasting to extend RI forecasting to time-dependent seismicity, for example, during an aftershock sequence. Nowcasting uses ‘natural time’; in seismicity natural time is the event count of small earthquakes. The event count for small earthquakes is extrapolated to larger earthquakes using Gutenberg–Richter scaling. We first review the concepts of natural time and nowcasting and then illustrate seismic nowcasting with three examples. We first consider the aftershock sequence of the 2004 Parkfield earthquake on the San Andreas fault in California. Some earthquakes have higher rates of aftershock activity than other earthquakes of the same magnitude. Our approach allows the determination of the rate in real time during the aftershock sequence. We also consider two examples of induced earthquakes. Large injections of waste water from petroleum extraction have generated high rates of induced seismicity in Oklahoma. The extraction of natural gas from the Groningen gas field in The Netherlands has also generated very damaging earthquakes. In order to reduce the seismic activity, rates of injection and withdrawal have been reduced in these two cases. We show how nowcasting can be used to assess the success of these efforts. This article is part of the theme issue ‘Statistical physics of fracture and earthquakes’.

scholarly journals MODELLING THE ENERGY RELEASE PROCESS OF AFTERSHOCKS

2017 ◽  
Vol 50 (3) ◽  
pp. 1341
Author(s):  
D. Gospodinov
Keyword(s):  
Stochastic Model ◽  
Energy Release ◽  
Aftershock Sequence ◽  
Suggested Model ◽  
Cumulative Energy ◽  
Release Process ◽  
Aftershock Sequences ◽  
Strain Release ◽  
Loma Prieta ◽  
Benioff Strain

A stochastic model for the study of Benioff strain release during aftershock sequences is suggested. The stochastic model is elaborated after a compound Poisson process and is applied on data of the M7.1 Ocober 18, 1989 Loma Prieta aftershock sequence in northern California, USA. The temporal evolution of the number of events is first modelled by the Restricted Epidemic Type Aftershock Sequence (RETAS) model and then the identified best fit model is incorporated in the energy release analysis. The suggested model is based on the assumptions that there is no relation between the magnitude and the occurrence time of an event first and second, that there is no relation between the magnitude of a certain event and magnitudes of previous events. The obtained results from the examination of the energy release reveal that the suggested model makes a good fit of the aftershock Benioff strain release and enables a more detailed study by identifying possible deviations between data and model. The real cumulative energy release values surpass the expected model ones, which proves that aftershocks, stronger than forecasted by the model, are clustered at the beginning of the Loma Prieta sequence.

Operational Aftershock Forecasting for 2017-2018 Seismic Sequence in Western Iran

2021 ◽  
Author(s):  
Fatemeh Jalayer ◽  
Hossein Ebrahimian
Keyword(s):  
Model Updating ◽  
Aftershock Sequence ◽  
Border Region ◽  
Model Parameters ◽  
Time Interval ◽  
Seismic Sequence ◽  
Epicentral Area ◽  
Western Iran ◽  
Spatio Temporal ◽  
Robust Reliability

<p>On Sunday November 12, 2017, at 18:18:16 UTC, (21:48:16 local time), a strong earthquake with Mw7.3 occurred in western Iran in the border region between Iran and Iraq in vicinity of the Sarpol-e Zahab town. Unfortunately, this catastrophic seismic event caused 572 causalities, thousands of injured and vast amounts of damage to the buildings, houses and infrastructures in the epicentral area. The mainshock of this seismic sequence was felt in the entire western and central provinces of Iran and surrounding areas. The main event was preceded by a foreshock with magnitude 4.5 about 43 minutes before the mainshock that warned the local residence to leave their home and possibly reduced the number of human casualties. More than 2500 aftershocks with magnitude greater than 2.5 have been reported up to January 2019 with the largest registered aftershock of Mw6.4. A novel and fully-probabilistic procedure is adopted for providing spatio-temporal predictions of aftershock occurrence in a prescribed forecasting time interval (in the order of hours or days). The procedure aims at exploiting the information provided by the ongoing seismic sequence in quasi-real time. The versatility of the Bayesian inference is exploited to adaptively update the forecasts based on the incoming information as it becomes available. The aftershock clustering in space and time is modelled based on an Epidemic Type Aftershock Sequence (ETAS). One of the main novelties of the proposed procedure is that it considers the uncertainties in the aftershock occurrence model and its model parameters. This is done by moving within a framework of robust reliability assessment which enables the treatment of uncertainties in an integrated manner. Pairing up the Bayesian robust reliability framework and the suitable simulation schemes (Markov Chain Monte Carlo Simulation) provides the possibility of performing the whole forecasting procedure with minimum (or no) need of human interference. The fully simulation-based procedure is examined for both Bayesian model updating of ETAS spatio-temporal model and robust operational forecasting of the number of events of interest expected to happen in various time intervals after main events within the sequence. The seismicity is predicted within a confidence interval from the mean estimate.</p>

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.

scholarly journals Damage Assessment of an SRC Frame-Core Tube Structure under the Action of a Main Aftershock Sequence

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Peng Wang ◽  
Qingxuan Shi ◽  
Feng Wang ◽  
Siusiu Guo
Keyword(s):  
Main Shock ◽  
Vulnerability Index ◽  
Aftershock Sequence ◽  
Time Interval ◽  
Demand Model ◽  
Core Tube ◽  
Repair Work ◽  
Damage Data ◽  
Probabilistic Seismic Demand ◽  
Tube Structure

Historical seismic damage data show that most strong earthquakes are accompanied by multiple intense aftershocks. In general, the time interval between the main shock and the aftershocks is relatively short, and structure repair work is often not completed before the aftershocks occur. For a structure that has suffered damage from the main shock, the aftershock will further aggravate the damage and even cause complete collapse. Based on the incremental dynamic analysis (IDA) method, this paper establishes a probabilistic seismic demand model for the SRC framework-core tube structure and plots the vulnerability curve of a structure under the action of the main aftershock sequence, which occurs following the actions of frequent earthquakes, fortification earthquakes, and rare earthquakes. The structure vulnerability matrix and the vulnerability index are used to evaluate the seismic performance of a structure. This study found that the occurrence of aftershocks leads the structure to a more unfavourable failure state. Taking the vulnerability index as an evaluation parameter, the structural vulnerability index when subjected to an intensity 8 earthquake under the action of the main aftershock is approximately 10% larger than under the action of a single main shock. Meanwhile, the SRC frame-core structure designed according to the current Chinese specifications meets the expected seismic fortification target, even after being acted upon by the main aftershock ground motion sequence.

scholarly journals The aftershock sequence of the north-west Kashmir earthquake of September 3, 1972

2010 ◽  
Vol 28 (2-3) ◽  
Author(s):  
V. K. SRIVASTAVA ◽  
R. K. S. CHOUHAN ◽  
R. NIGAM
Keyword(s):  
Upper Mantle ◽  
B Value ◽  
Aftershock Sequence ◽  
Creep Recovery ◽  
Average Strain ◽  
Shear Creep ◽  
Kashmir Earthquake ◽  
North West ◽  
The North ◽  
Total Average

This paper is an attempt to study the aftershock sequence of the Northwest Kashmir earthquake of September 3, 1972. b value of the sequence is 1.59. The area of active strain zone is approximately 2.9 • ]013 sq. cm. The total average strain, average elastic energy and average stress of the rock before slip are 3.3 • 10~5, 3.2 ergs/cm3 and 19.8 kg/cm2. The strain rebound curve of the sequence has been constructed which shows a dual type of recovery where the compressional elastic creep is followed by the shear creep recovery. The relaxation time of the sequence is about 0.7 day, showing the Kelvin body like behaviour of the upper mantle.

scholarly journals Global statistics of aftershocks following large earthquakes: independence of times and magnitudes

2019 ◽  
pp. 67-76 ◽  
Author(s):  
S. V. Baranov ◽  
P. N. Shebalin
Keyword(s):  
Branching Processes ◽  
Large Data ◽  
Aftershock Sequence ◽  
Power Law Distribution ◽  
Aftershock Activity ◽  
Data Set ◽  
Omori Law ◽  
Main Shocks ◽  
The Times ◽  
Global Statistics

This paper considers the global statistics of times of largest aftershocks relative to the times of the corresponding main shocks. A large data set was used to show that the time-dependent distribution of largest aftershocks obeys a power law distribution. This is analogous to the Omori law for the sequence of all after- shocks. It is also shown that the times of the second, etc., largest aftershocks obey the same distribution. Thereby, we have confirmed the hypothesis that the times and magnitudes in an aftershock sequence are independent and make a good case for the Reasenberg-Jones representation of the aftershock process as a superposition of the Omori-Utsu law and the Gutenberg–Richter relation. Events that are smaller than the largest in an aftershock sequence show no delay relative to the largest event; this rejects the idea of the after- shock process as a direct failure cascade involving gradual transitions from larger to lesser scales, which imposes certain restrictions on the widely popular stochastic models of aftershock generation as branching processes. The above result is important in practice for prediction of aftershock activity and for assessing the hazard of large aftershocks.

scholarly journals A study of aftershocks of 20 October 1991 Uttarkashi earthquake

MAUSAM ◽  
2022 ◽  
Vol 46 (4) ◽  
pp. 435-444
Author(s):  
R S. DATTATRAYAM ◽  
V.P. KAMBLE
Keyword(s):  
Decay Constant ◽  
Source Parameters ◽  
Temporal Distribution ◽  
B Value ◽  
Aftershock Sequence ◽  
Himalayan Region ◽  
Aftershock Activity ◽  
Field Surveys ◽  
Macroseismic Observations ◽  
Good Agreement

The Uttarkashi earthquake of 20 October 1991, which caused widespread damage in the Galhwal Himalayan region, was followed by a prominent aftershock. activity extending over a period of about two months. The aftershock activity was monitored using temporary networks established after the mainshock and the permanent stations in operation in the region. About 142 aftershocks could be located accurately using the data of these stations. The b-value of the Gutenberg-Richter's relationship for the aftershock sequence works out to be 0.6. The temporal distribution of the aftershocks suggests a hyperbolic decay with a decay constant (p) of 1.17. Macroseismic observations derived from field surveys show good agreement with the instrumentally determined source parameters.  

scholarly journals The East Aegean Sea strong earthquake sequence of October–November 2005: lessons learned for earthquake prediction from foreshocks

2006 ◽  
Vol 6 (6) ◽  
pp. 895-901 ◽  
Author(s):  
G. A. Papadopoulos ◽  
I. Latoussakis ◽  
E. Daskalaki ◽  
G. Diakogianni ◽  
A. Fokaefs ◽  
...  
Keyword(s):  
Seismic Analysis ◽  
Strong Shock ◽  
Aegean Sea ◽  
B Value ◽  
Aftershock Sequence ◽  
Lessons Learned ◽  
Time Interval ◽  
Aftershock Sequences ◽  
Duration Magnitude ◽  
Foreshock Activity

Abstract. The seismic sequence of October–November 2005 in the Samos area, East Aegean Sea, was studied with the aim to show how it is possible to establish criteria for (a) the rapid recognition of both the ongoing foreshock activity and the mainshock, and (b) the rapid discrimination between the foreshock and aftershock phases of activity. It has been shown that before the mainshock of 20 October 2005, foreshock activity is not recognizable in the standard earthquake catalogue. However, a detailed examination of the records in the SMG station, which is the closest to the activated area, revealed that hundreds of small shocks not listed in the standard catalogue were recorded in the time interval from 12 October 2005 up to 21 November 2005. The production of reliable relations between seismic signal duration and duration magnitude for earthquakes included in the standard catalogue, made it possible to use signal durations in SMG records and to determine duration magnitudes for 2054 small shocks not included in the standard catalogue. In this way a new catalogue with magnitude determination for 3027 events was obtained while the standard catalogue contains 1025 events. At least 55 of them occurred from 12 October 2005 up to the occurrence of the two strong foreshocks of 17 October 2005. This implies that foreshock activity developed a few days before the strong shocks of 17 October 2005 but it escaped recognition by the routine procedure of seismic analysis. The onset of the foreshock phase of activity is recognizable by the significant increase of the mean seismicity rate which increased exponentially with time. According to the least-squares approach the b-value of the magnitude-frequency relation dropped significantly during the foreshock activity with respect to the b-value prevailing in the declustered background seismicity. However, the maximum likelihood approach does not indicate such a drop of b. The b-value found for the aftershocks that followed the strong shock of 20 October 2005 is significantly higher than in foreshocks. The significant aftershock-foreshock difference in b-value is valid not only if the entire aftershock sequence is considered but also if only the segment of aftershocks that occurred within the first 24-h or the first 48-h after the mainshock of 20 October 2005 are taken into account. This difference in b-value should be examined further in other foreshock-aftershock sequences because it could be used as a diagnostic of the mainshock occurrence within a few hours after its generation.

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