An Application Of The Aftershock Probability Evaluation Methods For Recent Albania Earthquakes Based On Gutenberg-Richter And Modified Omori Models (original) (raw)
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Statistical evaluation and probabilistic modeling of aftershock sequences of Iranian plateau
Journal of Seismology, 2018
The present research focuses on the statistical evaluation of Iranian plateau aftershocks from an engineering perspective and presents probabilistic models applicable for generating random earthquake scenarios. Accordingly, a comprehensive earthquake data catalog including the period from 1964 to 2016 is prepared. Data are declustered into 37 separate mainshock-aftershock sequences by considering the completeness moment magnitude of the database. The well-known modified Omori occurrence rate formula is adopted to determine the recurrence time of the events, considering the effect of secondary aftershocks. In addition to computing the probability density functions of the parameters of the Omori formula, the joint probability distribution of the aftershock occurrence versus magnitude and occurrence time is obtained for modeling their magnitude sequences. The obtained results are applicable for producing randomly generated mainshockaftershock scenarios.
2018
Forecasting aftershock probabilities or forecasting the expected number of aftershocks, immediately after occurrence of an earthquake with a specified magnitude, is very important in risk management. The EpidemicType Aftershock Sequence (ETAS) model is a prominent stochastic model which describes the occurrence of earthquake sequences. However, this model has never been used to forecast aftershocks in Iran. Bushehr province in southern Iran has a long coastline onto the Persian Gulf and is one of the most strategic regions in the Middle East due to its major petroleum exporting ports, the industrial corridors and of course Bushehr Nuclear Power Plant. Bushehr is located in Zagros seismic region of Iran plateau. The earthquakes in this region often have a shallow focal depth and a reverse faulting mechanism. In this study, we simulate and estimate the number of aftershocks of the Mw 6.3 earthquake that took place in this region on April 9,2013, using the ETAS model. An earthquake cat...
2015
The main goal of this article is to study the Zagros aftershock decay rates. For this propose, the Iranian earthquake catalogue has been collected and homogenized between 2002 to 2014. Eight prominent earthquakes in the Zagros region were selected for aftershock decay rate study. Completeness magnitude and its variation was determined for each event. In order to investigate the behavior of aftershocks in the Zagros seismotectonic province, the Omori law parameters were calculated for selected events. Then, probabilistic aftershock hazard assessment (PAHA) based on aftershock parameters (a, b, P, K) of the 2013 April 9 Shonbe earthquake, has been estimated in temporal duration of 14, 30 and 60 days. In order to evaluate the variation of peak ground acceleration with time in the Zagros region, present attenuation relations and NGA formula has been applied. For calculating the PGA variations with time in 33% probability, we used logic tree for weighing different equation.
Geophysical Journal International, 2012
Although no deterministic and reliable earthquake precursor is known to date, we are steadily gaining insight into probabilistic forecasting that draws on space-time characteristics of earthquake clustering. Clustering-based models aiming to forecast earthquakes within the next 24 hours are under test in the global project 'Collaboratory for the Study of Earthquake Predictability' (CSEP). The 2011 March 11 magnitude 9.0 Tohoku-Oki earthquake in Japan provides a unique opportunity to test the existing 1-day CSEP models against its unprecedentedly active aftershock sequence. The original CSEP experiment performs tests after the catalogue is finalized to avoid bias due to poor data quality. However, this study differs from this tradition and uses the preliminary catalogue revised and updated by the Japan Meteorological Agency (JMA), which is often incomplete but is immediately available. This study is intended as a first step towards operability-oriented earthquake forecasting in Japan. Encouragingly, at least one model passed the test in most combinations of the target day and the testing method, although the models could not take account of the megaquake in advance and the catalogue used for forecast generation was incomplete. However, it can also be seen that all models have only limited forecasting power for the period immediately after the quake. Our conclusion does not change when the preliminary JMA catalogue is replaced by the finalized one, implying that the models perform stably over the catalogue replacement and are applicable to operational earthquake forecasting. However, we emphasize the need of further research on model improvement to assure the reliability of forecasts for the days immediately after the main quake. Seismicity is expected to remain high in all parts of Japan over the coming years. Our results present a way to answer the urgent need to promote research on time-dependent earthquake predictability to prepare for subsequent large earthquakes in the near future in Japan.
Probabilistic seismic hazard analysis of events occurred in Albania
2016
Albania is a seismic region so the goal of many earthquake engineers is to ensure the durability of a structure for a given level of ground vibration. There are many uncertainties about magnitude, location and the intensity of the future earthquake. Probability methods allow us to speak quantitatively about variables phenomenon. Probabilistic Seismic Hazard Analysis (PSHA) aims to reveal these uncertain and to produce the distribution of the future earthquakes that may occur. The purpose of this paper is to discuss the calculation involved in PSHA and to give some qualifications about the probability of intense ground vibration at a place and their associated rates of exceedance. The results can be used to identify the ground vibration intensity, which has small probability of being exceeded. In calculation are involved the location and intensity of all the seismic events occurred in Albania.
Natural Hazards, 1999
In order to investigate the effect of aftershocks on earthquake hazard estimation, earthquake hazard parameters (λm, b and Mmax) have been estimated by the maximum likelihood method from the main shocks catalogue and the raw earthquakes catalogue for the North Anatolian Fault Zone (NAFZ). The main shocks catalogue has been compiled from the raw earthquake catalogue by eliminating the aftershocks using the window method. The raw earthquake catalogue consisted of instrumentally detected earthquakes between 1900 and 1992, and historical earthquakes that occurred between 1000–1900. For the events of the mainshock catalogue the Poisson process is valid and for the raw earthquake catalogue it does not fit. The paper demonstrates differences in the hazard outputs if on one hand the main catalogues and on the other hand the raw catalogue is used. The maximum likelihood method which allows the use of the mixed earthquake catalogue containing incomplete (historical) and complete (instrumental) earthquake data is used to determine the earthquake hazard parameters. The maximum regional magnitude (Mmax, the seismic activity rate (λm), the mean return period (R) and the b value of the magnitude-frequency relation have been estimated for the 24°–31° E, 31°–41° E, 41°–45° E sections of the North Anatolian Fault Zone from the raw earthquake catalogue and the main shocks catalogue. Our results indicate that inclusion of aftershocks changes the b value and the seismic activity rate λm depending on the proportion of aftershocks in a region while it does not significantly effect the value of the maximum regional magnitude since it is related to the maximum observed magnitude. These changes in the earthquake hazard parameters caused the return periods to be over- and underestimated for smaller and larger events, respectively.
Journal of Seismology, 2010
A stochastic triggering (epidemic) model incorporating short-term clustering was fitted to the instrumental earthquake catalog of Italy for event with local magnitudes 2.6 and greater to optimize its ability to retrospectively forecast 33 target events of magnitude 5.0 and greater that occurred in the period 1990-2006. To obtain an unbiased evaluation of the information value of the model, forecasts of each event use parameter values obtained from data up to the end of the year preceding the target event. The results of the test are given in terms of the probability gain of the epidemic-type aftershock sequence (ETAS) model relative to a time-invariant Poisson model for each of the 33 target events. These probability gains range from 0.93 to 32000, with ten of the target events yielding a probability gain of at least 10. As the forecasting capability of the ETAS model is based on seismic activity recorded prior to the target earthquakes, the highest probability gains are associated with the occurrence of secondary R. Console · M. Murru (B) · G. Falcone mainshocks during seismic sequences. However, in nine of these cases, the largest mainshock of the sequence was marked by a probability gain larger than 50, having been preceded by previous smaller magnitude earthquakes. The overall evaluation of the performance of the epidemic model has been carried out by means of four popular statistical criteria: the relative operating characteristic diagram, the R score, the probability gain, and the log-likelihood ratio. These tests confirm the superior performance of the method with respect to a spatially varying, time-invariant Poisson model. Nevertheless, this method is characterized by a high false alarm rate, which would make its application in real circumstances problematic.
Aftershock Hazard Magnitude, Time, and Location Probability Forecasting
This study combines branching aftershock sequence (BASS) and modified Omori's law to develop a predictive model for forecasting the magnitude, time, and location of aftershocks of magnitude M w ≥ 5.00 in large earthquakes. The developed model is presented and applied to the 17:47 20 September 1999 M w 7.45 Chi-Chi earthquake Taiwan, 09:32 5 November 2009 (UTC) Nantou M w 6.19, 00:18 4 March 2010 (UTC) Jiashian M w 6.49 earthquake sequences, Taiwan, and 05:46 11 March 2011 (UTC) Tohoku M w 9.00 earthquake, Japan. The estimated peak ground acceleration (PGA) results are remarkably similar to calculations from the recorded magnitudes in both trend and level. This study proposes an empirical equation to improve the aftershock occurrence forecast time. The forecast time results were greatly improved. The magnitude of aftershocks generally decreases with time. It was found that the aftershock forecast probability of M w ≥ 5.00 is high in the first six days after the main shock. The results will be of interest to seismic mitigation specialists. Spatial and temporal seismicity parameters to the aftershock sequence investigation into the 17:47 20 September 1999 (UTC) M w 7.45 Chi-Chi earthquake, Taiwan found that immediately after the earthquake the area closest to the epicenter had a lower b value. This pattern suggests that at the time of the Chi-Chi earthquake, the area closest to the epicenter remained prone to large magnitude aftershocks and strong shaking. With time, however, the b value increased, indicating a reduced likelihood for large magnitude aftershocks.
Properties of the Aftershock Sequences of the 2003 Bingöl, M D = 6.4, (Turkey) Earthquake
Pure and Applied Geophysics, 2008
Aftershock sequences of the magnitude M W =6.4 Bingöl earthquake of 1 May, 2003 (Turkey) are studied to analyze the spatial and temporal variability of seismicity parameters of the b value of the frequency-magnitude distribution and the p value describing the temporal decay rate of aftershocks. The catalog taken from the KOERI contains 516 events and one month’s time interval. The b value is found as 1.49 ± 0.07 with Mc =3.2. Considering the error limits, b value is very close to the maximum b value stated in the literature. This larger value may be caused by the paucity of the larger aftershocks with magnitude M D ≥ 5.0. Also, the aftershock area is divided into four parts in order to detect the differences in b value and the changes illustrate the heterogeneity of the aftershock region. The p value is calculated as 0.86 ± 0.11, relatively small. This small p value may be a result of the slow decay rate of the aftershock activity and the small number of aftershocks. For the fitting of a suitable model and estimation of correct values of decay parameters, the sequence is also modeled as a background seismicty rate model. Constant background activity does not appear to be important during the first month of the Bingöl aftershock sequences and this result is coherent with an average estimation of pre-existing seismicity. The results show that usage of simple modified Omori law is reasonable for the analysis. The spatial variability in b value is between 1.2 and 1.8 and p value varies from 0.6 to 1.2. Although the physical interpretation of the spatial variability of these seismicity parameters is not straightforward, the variation of b and p values can be related to the stress and slip distribution after the mainshock, respectively. The lower b values are observed in the high stress regions and to a certain extent, the largest b values are related to Holocene alluvium. The larger p values are found in some part of the aftershock area although no slip occurred after the main shock and it is interpreted that this situation may be caused by the alluvium structure of the region. These results indicate that the spatial distribution in b and p values are generally related to the rupture mechanism and material properties of an aftershock area.
A quantitative study of some aftershock sequences in greece
Pure and Applied Geophysics PAGEOPH, 1994
Temporal features of the aftershock activities following twelve moderate shallow earthquakes in Greece have been studied quantitatively, by making use of the modified Omori's formula and Akaike's Information Criterion (AIC).