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1.
The Iranian Plateau does not appear to be a single crustal block, but an assemblage of zones comprising the Alborz—Azerbaijan, Zagros, Kopeh—Dagh, Makran, and Central and East Iran. The Gumbel’s III asymptotic distribution method (GIII) and maximum magnitude expected by Kijko—Sellevoll method is applied in order to check the potentiality of the each seismogenic zone in the Iranian Plateau for the future occurrence of maximum magnitude (Mmax). For this purpose, a homogeneous and complete seismicity database of the instrumental period during 1900–2012 is used in 29 seismogenic zones of the examined region. The spatial mapping of hazard parameters (upper bound magnitude (ω), most probable earthquake magnitude in next 100 years (M100) and maximum magnitude expected by maximum magnitude estimated by Kijko—Sellevoll method (max MK ? Smax) reveals that Central and East Iran, Alborz and Azerbaijan, Kopeh—Dagh and SE Zagros are a dangerous place for the next occurrence of a large earthquake.  相似文献   

2.
One of the crucial components in seismic hazard analysis is the estimation of the maximum earthquake magnitude and associated uncertainty. In the present study, the uncertainty related to the maximum expected magnitude μ is determined in terms of confidence intervals for an imposed level of confidence. Previous work by Salamat et al. (Pure Appl Geophys 174:763-777, 2017) shows the divergence of the confidence interval of the maximum possible magnitude mmax for high levels of confidence in six seismotectonic zones of Iran. In this work, the maximum expected earthquake magnitude μ is calculated in a predefined finite time interval and imposed level of confidence. For this, we use a conceptual model based on a doubly truncated Gutenberg-Richter law for magnitudes with constant b-value and calculate the posterior distribution of μ for the time interval Tf in future. We assume a stationary Poisson process in time and a Gutenberg-Richter relation for magnitudes. The upper bound of the magnitude confidence interval is calculated for different time intervals of 30, 50, and 100 years and imposed levels of confidence α?=?0.5, 0.1, 0.05, and 0.01. The posterior distribution of waiting times Tf to the next earthquake with a given magnitude equal to 6.5, 7.0, and 7.5 are calculated in each zone. In order to find the influence of declustering, we use the original and declustered version of the catalog. The earthquake catalog of the territory of Iran and surroundings are subdivided into six seismotectonic zones Alborz, Azerbaijan, Central Iran, Zagros, Kopet Dagh, and Makran. We assume the maximum possible magnitude mmax?=?8.5 and calculate the upper bound of the confidence interval of μ in each zone. The results indicate that for short time intervals equal to 30 and 50 years and imposed levels of confidence 1???α?=?0.95 and 0.90, the probability distribution of μ is around μ?=?7.16???8.23 in all seismic zones.  相似文献   

3.
Recent developments of the Middle East catalog   总被引：8，自引：2，他引：6  
This article summarizes a recent study in the framework of the Global Earth model (GEM) and the Earthquake Model of the Middle East (EMME) project to establish the new catalog of seismicity for the Middle East, using all historical (pre-1900), early and modern instrumental events up to 2006. According to different seismicity, which depends on geophysical, geological, tectonic, and seismicity data, this region is subdivided to nine subregions, consisting of Alborz–Azerbaijan, Afghanistan–Pakistan, Saudi Arabia, Caucasus, Central Iran, Kopeh–Dagh, Makran, Zagros, and Turkey (Eastern Anatolia; after 30° E). After omitting the duplicate events, aftershocks, and foreshocks by using the Gruenthal method, and uniform all magnitude to Mw scale, 28,244 main events remain for the new catalog of Middle East from 1250 B.C. through 2006. The magnitude of completeness (Mc) was determined as 4.9 for five out of nine subregions, where the least values of Mc were found to be 4.2. The threshold of Mc is around 5.5, 5.0, 4.5, and 4.0, for the time after 1950, 1963, 1975, and 2000, respectively. The average of teleseismic depths in all regions is less than 15 km. Totally, majority of depth for Kopeh–Dagh and Central Iran, Zagros, and Alborz–Azerbaijan, approximately, is 15, 13, and 11 km and for Afghanistan–Pakistan, Caucasus, Makran, Turkey (after 30° E), and Saudi Arabia is about 9 km.  相似文献   

4.
Two zones of seismicity (ten events with M w = 7.0–7.7) stretching from Makran and the Eastern Himalaya to the Central and EasternTien Shan, respectively, formed over 11 years after the great Makran earthquake of 1945 (M w = 8.1). Two large earthquakes (M w = 7.7) hit theMakran area in 2013. In addition, two zones of seismicity (M ≥ 5.0) occurred 1–2 years after theMakran earthquake in September 24, 2013, stretching in the north-northeastern and north-northwestern directions. Two large Nepal earthquakes struck the southern extremity of the “eastern” zone (April 25, 2015, M w = 7.8 and May 12, 2015, M w = 7.3), and the Pamir earthquake (December 7, 2015, M w = 7.2) occurred near Sarez Lake eastw of the “western” zone. The available data indicate an increase in subhorizontal stresses in the region under study, which should accelerate the possible preparation of a series of large earthquakes, primarily in the area of the Central Tien Shan, between 70° and 79° E, where no large earthquakes (M w ≥ 7.0) have occurred since 1992.  相似文献   

5.
Rapid magnitude estimation relations for earthquake early warning systems in the Alborz region have been developed based on the initial first seconds of the P-wave arrival. For this purpose, a total of 717 accelerograms recorded by the Building and Housing Research Center in the Alborz region with the magnitude (Mw) range of 4.8–6.5 in the period between 1995 and 2013 were employed. Average ground motion period (\( \tau_{\text{c}} \)) and peak displacement (\( P_{\text{d}} \)) in different time windows from the P-wave arrival were calculated, and their relation with magnitude was examined. Four earthquakes that were excluded from the analysis process were used to validate the results, and the estimated magnitudes were found to be in good agreement with the observed ones. The results show that using the proposed relations for the Alborz region, earthquake magnitude could be estimated with acceptable accuracy even after 1 s of the P-wave arrival.  相似文献   

6.
To study the prospective areas of upcoming strong-to-major earthquakes, i.e., M w  ≥ 6.0, a catalog of seismicity in the vicinity of the Thailand-Laos-Myanmar border region was generated and then investigated statistically. Based on the successful investigations of previous works, the seismicity rate change (Z value) technique was applied in this study. According to the completeness earthquake dataset, eight available case studies of strong-to-major earthquakes were investigated retrospectively. After iterative tests of the characteristic parameters concerning the number of earthquakes (N) and time window (T w ), the values of 50 and 1.2 years, respectively, were found to reveal an anomalous high Z-value peak (seismic quiescence) prior to the occurrence of six out of the eight major earthquake events studied. In addition, the location of the Z-value anomalies conformed fairly well to the epicenters of those earthquakes. Based on the investigation of correlation coefficient and the stochastic test of the Z values, the parameters used here (N = 50 events and T w  = 1.2 years) were suitable to determine the precursory Z value and not random phenomena. The Z values of this study and the frequency-magnitude distribution b values of a previous work both highlighted the same prospective areas that might generate an upcoming major earthquake: (i) some areas in the northern part of Laos and (ii) the eastern part of Myanmar.  相似文献   

7.
We present the seismic source zoning of the tectonically active Greater Kashmir territory of the Northwestern Himalaya and seismicity analysis (Gutenberg-Richter parameters) and maximum credible earthquake (m max) estimation of each zone. The earthquake catalogue used in the analysis is an extensive one compiled from various sources which spans from 1907 to 2012. Five seismogenic zones were delineated, viz. Hazara-Kashmir Syntaxis, Karakorum Seismic Zone, Kohistan Seismic Zone, Nanga Parbat Syntaxis, and SE-Kashmir Seismic Zone. Then, the seismicity analysis and maximum credible earthquake estimation were carried out for each zone. The low b value (<1.0) indicates a higher stress regime in all the zones except Nanga Parbat Syntaxis Seismic Zone and SE-Kashmir Seismic Zone. The m max was estimated following three different methodologies, the fault parameter approach, convergence rates using geodetic measurements, and the probabilistic approach using the earthquake catalogue and is estimated to be M w 7.7, M w 8.5, and M w 8.1, respectively. The maximum credible earthquake (m max) estimated for each zone shows that Hazara Kashmir Syntaxis Seismic Zone has the highest m max of M w 8.1 (±0.36), which is espoused by the historical 1555 Kashmir earthquake of M w 7.6 as well as the recent 8 October 2005 Kashmir earthquake of M w 7.6. The variation in the estimated m max by the above discussed methodologies is obvious, as the definition and interpretation of the m max change with the method. Interestingly, historical archives (～900 years) do not speak of a great earthquake in this region, which is attributed to the complex and unique tectonic and geologic setup of the Kashmir Himalaya. The convergence is this part of the Himalaya is distributed not only along the main boundary faults but also along the various active out-of-sequence faults as compared to the Central Himalaya, where it is mainly adjusted along the main boundary fault.  相似文献   

8.
Temporal distribution of earthquakes with M w > 6 in the Dasht-e-Bayaz region, eastern Iran has been investigated using time-dependent models. Based on these types of models, it is assumed that the times between consecutive large earthquakes follow a certain statistical distribution. For this purpose, four time-dependent inter-event distributions including the Weibull, Gamma, Lognormal, and the Brownian Passage Time (BPT) are used in this study and the associated parameters are estimated using the method of maximum likelihood estimation. The suitable distribution is selected based on logarithm likelihood function and Bayesian Information Criterion. The probability of the occurrence of the next large earthquake during a specified interval of time was calculated for each model. Then, the concept of conditional probability has been applied to forecast the next major (M w > 6) earthquake in the site of our interest. The emphasis is on statistical methods which attempt to quantify the probability of an earthquake occurring within a specified time, space, and magnitude windows. According to obtained results, the probability of occurrence of an earthquake with M w > 6 in the near future is significantly high.  相似文献   

9.
The 2017 Guptkashi earthquake occurred in a segment of the Himalayan arc with high potential for a strong earthquake in the near future. In this context, a careful analysis of the earthquake is important as it may shed light on source and ground motion characteristics during future earthquakes. Using the earthquake recording on a single broadband strong-motion seismograph installed at the epicenter, we estimate the earthquake’s location (30.546° N, 79.063° E), depth (H?=?19 km), the seismic moment (M0?=?1.12×1017 Nm, M w 5.3), the focal mechanism (φ?=?280°, δ?=?14°, λ?=?84°), the source radius (a?=?1.3 km), and the static stress drop (Δσ s ~22 MPa). The event occurred just above the Main Himalayan Thrust. S-wave spectra of the earthquake at hard sites in the arc are well approximated (assuming ω?2 source model) by attenuation parameters Q(f)?=?500f0.9, κ?=?0.04 s, and fmax?=?infinite, and a stress drop of Δσ?=?70 MPa. Observed and computed peak ground motions, using stochastic method along with parameters inferred from spectral analysis, agree well with each other. These attenuation parameters are also reasonable for the observed spectra and/or peak ground motion parameters in the arc at distances ≤?200 km during five other earthquakes in the region (4.6?≤?M w ?≤?6.9). The estimated stress drop of the six events ranges from 20 to 120 MPa. Our analysis suggests that attenuation parameters given above may be used for ground motion estimation at hard sites in the Himalayan arc via the stochastic method.  相似文献   

10.
Recent studies have shown that the vertical component of ground motion can be quite destructive on a variety of structural systems. Development of response spectrum for design of buildings subjected to vertical component of earthquake needs ground motion prediction equations (GMPEs). The existing GMPEs for northern Iranian plateau are proposed for the horizontal component of earthquake, and there is not any specified GMPE for the vertical component of earthquake in this region. Determination of GMPEs is mostly based on regression analyses on earthquake parameters such as magnitude, site class, distance, and spectral amplitudes. In this study, 325 three-component records of 55 earthquakes with magnitude ranging from M w 4.1 to M w 7.3 are used for estimation on the regression coefficients. Records with distances less than 300 km are selected for analyses in the database. The regression analyses on earthquake parameters results in determination of GMPEs for peak ground acceleration and spectral acceleration for both horizontal and vertical components of the ground motion. The correlation between the models for vertical and horizontal GMPEs is studied in details. These models are later compared with some other available GMPEs. According to the result of this investigation, the proposed GMPEs are in agreement with the other relationships that were developed based on the local and regional data.  相似文献   

11.
Attenuation of P and S waves has been investigated in Alborz and north central part of Iran using the data recorded by two permanent and one temporary networks during October 20, 2009, to December 22, 2010. The dataset consists of 14,000 waveforms from 380 local earthquakes (2 < M L < 5.6). The extended coda normalization method (CNM) was used to estimate quality factor of P (Q P) and S waves (Q S) at seven frequency bands (0.375, 0.75, 1.5, 3, 6, 12, 24 Hz). The Q P and Q S values have been estimated at lapse times from 40 to 100 s. It has been observed that the estimated values of Q P and Q S are time independent; therefore, the mean values of Q P and Q S at different lapse times have been considered. The frequency dependence of quality factor was determined by using a power-law relationship. The frequency-dependent relationship for Q P was estimated in the form of (62 ± 7)f (1.03 ± 0.07) and (48 ± 5)f (0.95 ± 0.07) in Alborz region and North Central Iran, respectively. These relations for Q S for Alborz region and North Central Iran have estimated as (83 ± 8)f (0.99 ± 0.07) and (68 ± 5)f (0.96 ± 0.05), respectively. The observed low Q values could be the results of thermoelastic effects and/or existing fracture. The estimated frequency-dependent relationships are comparable with tectonically active regions.  相似文献   

12.
Aftershock hazard maps contain the essential information for search and rescue process, and re-occupation after a main-shock. Accordingly, the main purposes of this article are to study the aftershock decay parameters and to estimate the expected high-frequency ground motions (i.e., Peak Ground Acceleration (PGA)) for recent large earthquakes in the Iranian plateau. For this aim, the Ahar-Varzaghan doublet earthquake (August 11, 2012; M N =6.5, M N =6.3), and the Ilam (Murmuri) earthquake (August 18, 2014 ; M N =6.2) have been selected. The earthquake catalogue has been collected based on the Gardner and Knopoff (Bull Seismol Soc Am 64(5), 1363-1367, 1974) temporal and spatial windowing technique. The magnitude of completeness and the seismicity parameters (a,??b) and the modified Omori law parameters (P,??K,??C) have been determined for these two earthquakes in the 14, 30, and 60 days after the mainshocks. Also, the temporal changes of parameters (a,??b,??P,??K,??C) have been studied. The aftershock hazard maps for the probability of exceedance (33%) have been computed in the time periods of 14, 30, and 60 days after the Ahar-Varzaghan and Ilam (Murmuri) earthquakes. For calculating the expected PGA of aftershocks, the regional and global ground motion prediction equations have been utilized. Amplification factor based on the site classes has also been implied in the calculation of PGA. These aftershock hazard maps show an agreement between the PGAs of large aftershocks and the forecasted PGAs. Also, the significant role of b parameter in the Ilam (Murmuri) probabilistic aftershock hazard maps has been investigated.  相似文献   

13.
In this study, pre-seismic and post-seismic total electron content (TEC) anomalies of 63 Mw?≥?5.0 earthquakes in Turkey (36°–42°N, 26°–45°E) were statistically investigated. The largest earthquake that occurred in Turkey during 2003–2016 is the Mw 7.1 Van earthquake on October 23, 2011. The TEC data of epicenters is obtained from CODE-GIM using a simple 4-point bivariate interpolation. The anomalies of TEC variations were determined by using a quartile-based running median process. In order to validate GIM results, we used the GPS-TEC data of available four IGS stations within the size of the Van earthquake preparation area. The anomalies that are detected by GIM and GPS-TEC show a similar pattern. Accordingly, the results obtained with CODE-GIM are reliable. The statistical results show that there are not prominent earthquake precursors for Mw?≤?6.0 earthquakes in Turkey.  相似文献   

14.
An earthquake with the moment magnitude M w ?=?5.8 occurred in the middle part of the Sakhalin Island, Russian Federation, on 14 August 2016, at 11:17 a.m. UTC. The earthquake source was located west of the Central Sakhalin Fault Zone, which is considered to mark the boundary between the Okhotsk and Eurasian (Amurian) plates. Moment tensor solution of the mainshock as well as the configuration of aftershock cloud suggests that the earthquake was caused by slip on a SW-dipping reverse fault. For the first time for Sakhalin, we have got the felt reports unified in accordance with DYFI. We also analyzed observed PGA values and, based on them, produced shaking maps.  相似文献   

15.
This study analyzes and compares the P- and S-wave displacement spectra from local earthquakes and explosions of similar magnitudes. We propose a new approach to discrimination between low-magnitude shallow earthquakes and explosions by using ratios of P- to S-wave corner frequencies as a criterion. We have explored 2430 digital records of the Israeli Seismic Network (ISN) from 456 local events (226 earthquakes, 230 quarry blasts, and a few underwater explosions) of magnitudes Md?=?1.4–3.4, which occurred at distances up to 250 km during 2001–2013 years. P-wave and S-wave displacement spectra were computed for all events following Brune’s source model of earthquakes (1970, 1971) and applying the distance correction coefficients (Shapira and Hofstetter, Teconophysics 217:217–226, 1993; Ataeva G, Shapira A, Hofstetter A, J Seismol 19:389-401, 2015), The corner frequencies and moment magnitudes were determined using multiple stations for each event, and then the comparative analysis was performed.The analysis showed that both P-wave and especially S-wave displacement spectra of quarry blasts demonstrate the corner frequencies lower than those obtained from earthquakes of similar magnitudes. A clear separation between earthquake and explosion populations was obtained for ratios of P- to S-wave corner frequency f 0(P)/f 0(S). The ratios were computed for each event with corner frequencies f 0 of P- and S-wave, which were obtained from the measured f 0 I at individual stations, then corrected for distance and finally averaged. We obtained empirically the average estimation of f 0(P)/f 0(S)?=?1.23 for all used earthquakes, and 1.86 for all explosions. We found that the difference in the ratios can be an effective discrimination parameter which does not depend on estimated moment magnitude M w .The new multi-station Corner Frequency Discriminant (CFD) for earthquakes and explosions in Israel was developed based on ratios P- to S-wave corner frequencies f 0(P)/f 0(S), with the empirical threshold value of the ratio for Israel as 1.48.  相似文献   

16.
An important task in seismic hazard assessment is estimation of the intensity and frequency of extremely strong earthquake effects, in particular, peak ground velocities (PGV). Earlier, a method was proposed to evaluate PGV values based on the magnitude of displacements of rock blocks (Rodkin et al., 2012). In this study, this method is used to analyze field data on the source zones of the August 19, 1992, MS = 7.3 Susamyr earthquake and the January 3, 1911, Mw = 7.9 Kemin earthquake, and estimate maximum ground shaking at the upper construction site of the Upper Naryn series of hydropower plants, Kyrgyz Republic. It is shown that the resulting estimates are consistent with data obtained through other techniques. Therefore, the new approach can be recommended to estimate earthquake effects.  相似文献   

17.
We study the frictional and viscous effects on earthquake nucleation, especially for the nucleation phase, based on a one-degree-of-freedom spring-slider model with friction and viscosity. The frictional and viscous effects are specified by the characteristic displacement, U c, and viscosity coefficient, η, respectively. Simulation results show that friction and viscosity can both lengthen the natural period of the system and viscosity increases the duration time of motion of the slider. Higher viscosity causes a smaller amplitude of lower velocity motion than lower viscosity. A change of either U c (under large η) or η (under large U c) from a large value (U ch for U c and η h for η) to a small one (U cl for U c and η l for η) in two stages during sliding can result in a clear nucleation phase prior to the P-wave. The differences δU c = U ch ? U cl and δη = η h ? η l are two important factors in producing a nucleation phase. The difference between the nucleation phase and the P-wave increases with either δU c or δη. Like seismic observations, the peak amplitude of P-wave, which is associated with the earthquake magnitude, is independent upon the duration time of nucleation phase. A mechanism specified with a change of either η or U c from a larger value to a smaller one due to temporal variations in pore fluid pressure and temperature in the fault zone based on radiation efficiency is proposed to explain the simulation results and observations.  相似文献   

18.
The implications of the earthquakes that took place in the central Ionian Islands in 2014 (Cephalonia, M w6.1, M w5.9) and 2015 (Lefkas, M w6.4) are described based on repeat measurements of the local GPS networks in Cephalonia and Ithaca, and the available continuous GPS stations in the broader area. The Lefkas earthquake occurred on a branch of the Cephalonia Transform Fault, affecting Cephalonia with SE displacements gradually decreasing from north (~100 mm) to south (~10 mm). This earthquake revealed a near N–S dislocation boundary separating Paliki Peninsula in western Cephalonia from the rest of the island, as well as another NW–SE trending fault that separates kinematically the northern and southern parts of Paliki. Strain field calculations during the interseismic period (2014–2015) indicate compression between Ithaca and Cephalonia, while extension appears during the following co-seismic period (2015–2016) including the 2015 Lefkas earthquake. Additional tectonically active zones with differential kinematic characteristics were also identified locally.  相似文献   

19.
We propose a method that employs the squared displacement integral (ID2) to estimate earthquake magnitudes in real time for use in earthquake early warning (EEW) systems. Moreover, using τ c and P d for comparison, we establish formulas for estimating the moment magnitudes of these three parameters based on the selected aftershocks (4.0 ≤ M s  ≤ 6.5) of the 2008 Wenchuan earthquake. In this comparison, the proposed ID2 method displays the highest accuracy. Furthermore, we investigate the applicability of the initial parameters to large earthquakes by estimating the magnitude of the Wenchuan M s 8.0 mainshock using a 3-s time window. Although these three parameters all display problems with saturation, the proposed ID2 parameter is relatively accurate. The evolutionary estimation of ID2 as a function of the time window shows that the estimation equation established with ID2 Ref determined from the first 8-s of P wave data can be directly applicable to predicate the magnitudes of 8.0. Therefore, the proposed ID2 parameter provides a robust estimator of earthquake moment magnitudes and can be used for EEW purposes.  相似文献   

20.
The damping modification factor (DMF) has been extensively used in earthquake engineering to describe the variation of structural responses due to varied damping ratios. It is known that DMFs are dependent not only on structural dynamic properties but also on characteristics of ground motions. DMFs regulated in current seismic codes are generally developed based on far-fault ground motions and are inappropriately used in structural design where pulse-like near-fault ground motions are involved. In this paper, statistical investigation of the DMF is performed based on 50 carefully selected pulse-like near-fault ground motions. It is observed that DMFs for pulse-like ground motions exhibit significant dependence on the pulse period T p in a specific period range. If the period of the structure in response is close to the pulse period, the DMF attains the same level as that derived from far-fault ground motions; as the period of the structure is considerably larger or smaller than the pulse period T p , the response reduction effect by the increased damping ratio is generally small, except for large earthquakes with long pulse periods, which exhibit significant reduction of response for structures with periods smaller than T p . Based on the statistical results of DMFs, the empirical formulas for estimating DMFs for displacement, velocity and acceleration spectra are proposed, the effect of structural period, pulse period and damping ratio are considered in the formulas, and the formulas are designed to satisfy the specific reliability requirement in the period range of 0.1 < T/T p  < 1, which is of engineering interest.  相似文献   

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