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1.
The return periods and occurrence probabilities related to medium and large earthquakes (M w 4.0–7.0) in four seismic zones in northeast India and adjoining region (20°–32°N and 87°–100°E) have been estimated with the help of well-known extreme value theory using three methods given by Gumbel (1958), Knopoff and Kagan (1977) and Bury (1999). In the present analysis, the return periods, the most probable maximum magnitude in a specified time period and probabilities of occurrences of earthquakes of magnitude M ≥ 4.0 have been computed using a homogeneous and complete earthquake catalogue prepared for the period between 1897 and 2007. The analysis indicates that the most probable largest annual earthquakes are close to 4.6, 5.1, 5.2, 5.5 and 5.8 in the four seismic zones, namely, the Shillong Plateau Zone, the Eastern Syntaxis Zone, the Himalayan Thrusts Zone, the Arakan-Yoma subduction zone and the whole region, respectively. The most probable largest earthquakes that may occur within different time periods have been also estimated and reported. The study reveals that the estimated mean return periods for the earthquake of magnitude M w 6.5 are about 6–7 years, 9–10 years, 59–78 years, 72–115 years and 88–127 years in the whole region, the Arakan-Yoma subduction zone, the Himalayan Thrusts Zone, the Shillong Plateau Zone and the Eastern Syntaxis Zone, respectively. The study indicates that Arakan-Yoma subduction zone has the lowest mean return periods and high occurrence probability for the same earthquake magnitude in comparison to the other zones. The differences in the hazard parameters from zone to zone reveal the high crustal heterogeneity and seismotectonics complexity in northeast India and adjoining regions.  相似文献   

2.
Deterministic seismic microzonation of Kolkata city   总被引：1，自引：0，他引：1  
This paper presents the deterministic seismic microzonation of densely populated Kolkata city situated on the world’s largest delta island with very soft and thick soil deposit in the surficial layers. A fourth-order accurate staggered-grid finite-difference algorithm for SH-wave propagation simulation in visco-elastic medium is used for the linear computation of ground motion amplifications in sedimentary deposit. Different maps such as for fundamental frequency (F 0), peak ground acceleration (PGA), peak ground velocity, and peak ground displacement are developed for variety of end-users communities, including structural and geotechnical engineers for performance-based designs, building officials, emergency managers, land-use planners, private businesses, and the general public. The scenario of simulated amplification factors in the different frequency bands revealed that the Kolkata city is very much prone to severe damage even during a moderate earthquake and very selective damage may occur at some of the localities during local and distant earthquakes. The deterministically predicted PGA at bedrock level is 0.0844 g and the maximum PGA predicted at the free surface is 0.6 g in Kolkata city due to maximum credible earthquake (M w = 5.4) associated with Eocene Hinge Zone at a depth of 36 km. The seismic microzonation of Kolkata city reveals that the Nager Bazar and Nimtala areas are the safest regions with earthquake point of view.  相似文献   

3.
The assessment of local site effects on seismic ground motions is of great importance in earthquake engineering practice. Several destructive earthquakes in the past have demonstrated that the amplification of ground motion and associated damage to structures due to local site conditions is a significant consideration in earthquake hazard analysis. A recent paper published in this journal highlights the hazard posed by earthquakes in the megacity of Kolkata in India due to its seismic and geological settings. The seismic hazard assessment study speculates that the deep alluvial deposit in the city may increase the seismic hazard probably due to the amplification of the seismic energies. This paper focuses on the seismic response studies of the various soil strata (i.e. for local subsurface conditions) obtained from various construction sites in the city for predicted earthquake. It is very well recognized that site response studies (a part of seismic microhazard zonation for urban areas) are the first step towards performance-based foundation design or seismic risk analysis and mitigation strategy. One of the problems for carrying out site-specific study in Kolkata is the lack of recorded strong motion data in the city. Hence, this paper outlines a methodology to carry out site-specific study, where no strong motion data or seismic data are available. The methodology uses wavelet-based spectrum compatibility approach to generate synthetic earthquake motions and equivalent linear method for seismic site response analysis. The Mega City of Kolkata has been considered to explain the methodology. Seismic hazard zonation map by the Bureau of Indian Standards classifies the City of Kolkata as moderate seismic zone (Zone III) with a zone factor 0.16. On the other hand, GSHAP(Global Seismic Hazard Assessment Program) map which is based on 10% probability of exceedance in 50 years specifies a maximum peak ground acceleration (PGA) of 1.6 m/s2 (0.163 g) for this region. In the present study, the seismic response has been carried out based on GSHAP. The results of the analysis indicate the amplification of ground motion in the range of 4.46–4.82 with the fundamental period ranging from 0.81 to 1.17 s. Furthermore, the maximum spectral accelerations vary in the range of 0.78–0.95 g.  相似文献   

4.
Kolkata, capital of West Bengal, India, presently congested with moderate to high rise buildings, has undergone low to moderate damages due to past earthquakes. The city is situated on the world’s largest delta island with soft thick alluvial soil layer. In this study, an attempt has been made to study ground response due to a number of past earthquakes, 1897 Shillong earthquake, 1964 Calcutta earthquake and 2011 Sikkim earthquake, for the purpose of preliminary microzonation of the Kolkata city. For this, synthetic ground motions have been generated at bedrock level by stochastic method. By using 1D wave propagation technique, the synthetic ground motion has been computed at surface level for 144 borehole locations in the city. Contours of PGA, PGV and PGD parameters in the city have been drawn for these three earthquakes. Response spectra for these three earthquakes have also been computed and an optimum response spectrum has been determined. A good correlation has been obtained with predicted ground motion at surface level of the city with the reported intensity and damages occurred in buildings of Kolkata during past earthquakes. The scenario of simulated ground motion for the past three earthquakes depicts that Kolkata city is very much prone to damages even due to moderate far and near source earthquakes.  相似文献   

5.
Probabilistic seismic hazard analysis for Bangalore   总被引：5，自引：3，他引：2  
This article presents the results of probabilistic seismic hazard analysis (PSHA) for Bangalore, South India. Analyses have been carried out considering the seismotectonic parameters of the region covering a radius of 350 km keeping Bangalore as the center. Seismic hazard parameter ‘b’ has been evaluated considering the available earthquake data using (1) Gutenberg–Richter (G–R) relationship and (2) Kijko and Sellevoll (1989, 1992) method utilizing extreme and complete catalogs. The ‘b’ parameter was estimated to be 0.62 to 0.98 from G–R relation and 0.87 ± 0.03 from Kijko and Sellevoll method. The results obtained are a little higher than the ‘b’ values published earlier for southern India. Further, probabilistic seismic hazard analysis for Bangalore region has been carried out considering six seismogenic sources. From the analysis, mean annual rate of exceedance and cumulative probability hazard curve for peak ground acceleration (PGA) and spectral acceleration (Sa) have been generated. The quantified hazard values in terms of the rock level peak ground acceleration (PGA) are mapped for 10% probability of exceedance in 50 years on a grid size of 0.5 km × 0.5 km. In addition, Uniform Hazard Response Spectrum (UHRS) at rock level is also developed for the 5% damping corresponding to 10% probability of exceedance in 50 years. The peak ground acceleration (PGA) value of 0.121 g obtained from the present investigation is slightly lower (but comparable) than the PGA values obtained from the deterministic seismic hazard analysis (DSHA) for the same area. However, the PGA value obtained in the current investigation is higher than PGA values reported in the global seismic hazard assessment program (GSHAP) maps of Bhatia et al. (1999) for the shield area.  相似文献   

6.
The Indian subcontinent is characterized by various tectonic units viz., Himalayan collision zone in North, Indo-Burmese arc in north-east, failed rift zones in its interior in Peninsular Indian shield and Andaman Sumatra trench in south-east Indian Territory. During the last about 100 years, the country has witnessed four great and several major earthquakes. Soon after the occurrence of the first great earthquake, the Shillong earthquake (M w: 8.1) in 1897, efforts were started to assess the seismic hazard in the country. The first such attempt was made by Geological Survey of India in 1898 and since then considerable progress has been made. The current seismic zonation map prepared and published by Bureau of Indian Standards, broadly places seismic risk in different parts of the country in four major zones. However, this map is not sufficient for the assessment of area-specific seismic risks, necessitating detailed seismic zoning, that is, microzonation for earthquake disaster mitigation and management. Recently, seismic microzonation studies are being introduced in India, and the first level seismic microzonation has already been completed for selected urban centres including, Jabalpur, Guwahati, Delhi, Bangalore, Ahmadabad, Dehradun, etc. The maps prepared for these cities are being further refined on larger scales as per the requirements, and a plan has also been firmed up for taking up microzonation of 30 selected cities, which lie in seismic zones V and IV and have a population density of half a million. The paper highlights the efforts made in India so far towards seismic hazard assessment as well as the future road map for such studies.  相似文献   

7.
In this study, an attempt is made to determine seismic velocity structure of the crust and upper mantle beneath the Shillong-Mikir Hills Plateau in northeast India region. The principle of the technique is to relate seismic travel times with crustal thickness above the Conrad and Moho discontinuities. Broadband digital waveforms of the local earthquakes make a precise detection of the seismic phases possible that are reflected at these discontinuities. The results show that the Conrad discontinuity is at 18–20 (±0.5) km beneath the Shillong-Mikir Hills Plateau and the Moho discontinuity is at 30 ± 1.0 km beneath the Shillong Plateau and at 35 ± 1.0 km beneath the Mikir Hills.  相似文献   

8.
In the present study, the cumulative seismic energy released by earthquakes (M w ≥ 5) for a period of 1897 to 2009 is analyzed for northeast (NE) India. For this purpose, a homogenized earthquake catalogue in moment magnitude (M w ) has been prepared. Based on the geology, tectonics and seismicity, the study region is divided into three source zones namely, 1: Arakan-Yoma Zone (AYZ), 2: Himalayan Zone (HZ) and 3: Shillong Plateau Zone (SPZ). The maximum magnitude (M max ) for each source zone is estimated using Tsuboi’s energy blocked model. As per the energy blocked model, the supply of energy for potential earthquakes in an area is remarkably uniform with respect to time and the difference between the supply energy and cumulative energy released for a span of time, is a good indicator of energy blocked and can be utilized for the estimation of maximum magnitude (M max ) earthquakes. The proposed process provides a more consistent model of gradual accumulation of strain and non-uniform release through large earthquakes can be applied in the assessment of seismic hazard. Energy blocked for source zone 1, zone 2 and zone 3 regions is 1.35×1017 Joules, 4.25×1017 Joules and 7.25×1017 Joules respectively and will act as a supply for potential earthquakes in due course of time. The estimated M max for each source zone AYZ, HZ, and SPZ are 8.2, 8.6, and 8.7 respectively. M max obtained from this model is well comparable with the results of previous workers from NE region.  相似文献   

9.
The epicentral tract of the great Assam earthquake of 1897 of magnitude 8·7 was monitored for about 6 months using an array of portable seismographs. The observed seismicity pattern shows several diversely-oriented linear trends, some of which either encompass or parallel known geological faults. A vast majority of the recorded micro-earthquakes had estimated focal depths between 8–14 km. The maximum estimated depth was 45 km. On the basis of a seismic velocity model for the region reported recently and these depth estimates we suggest that the rupture zone of the great 1897 earthquake had a depth of 11–12 km under the western half of the Shillong massif. Four composite fault plane solutions define the nature of dislocation in three of the seismic zones. Three of them show oblique thrusting while one shows pure dip slip reverse faulting. The fault plane solutions fit into a regional pattern of a belt of earthquakes extending in NW-SE direction across the north eastern corner of the Bengal basin. The maximum principle stress axis is approximately NS for all the solutions in conformity with the inferred direction of the Indian-EuroAsian plate convergence in the eastern Himalaya.  相似文献   

10.
Seismic potential of Southern Italy   总被引：1，自引：2，他引：1  
To improve estimates of the long-term average seismic potential of the slowly straining South Central Mediterranean plate boundary zone, we integrate constraints on tectonic style and deformation rates from geodetic and geologic data with the traditional constraints from seismicity catalogs. We express seismic potential (long-term average earthquake recurrence rates as a function of magnitude) in the form of truncated Gutenberg–Richter distributions for seven seismotectonic source zones. Seismic coupling seems to be large or even complete in most zones. An exception is the southern Tyrrhenian thrust zone, where most of the African–European convergence is accommodated. Here aseismic deformation is estimated to range from at least 25% along the western part to almost 100% aseismic slip around the Aeolian Islands. Even so, seismic potential of this zone has previously been significantly underestimated, due to the low levels of recorded past seismicity. By contrast, the series of 19 M6–7 earthquakes that hit Calabria in the 18th and 19th century released tectonic strain rates accumulated over time spans up to several times the catalog duration, and seismic potential is revised downward. The southern Tyrrhenian thrust zone and the extensional Calabrian faults, as well as the northeastern Sicilian transtensional zone between them (which includes the Messina Straits, where a destructive M7 event occurred in 1908), all have a similar seismic potential with minimum recurrence times of M ≥ 6.5 of 150–220 years. This potential is lower than that of the Southern Apennines (M ≥ 6.5 recurring every 60 to 140 years), but higher than that of southeastern Sicily (minimum M ≥ 6.5 recurrence times of 400 years). The high seismicity levels recorded in southeastern Sicily indicate some clustering and are most compatible with a tectonic scenario where the Ionian deforms internally, and motions at the Calabrian Trench are small. The estimated seismic potential for the Calabrian Trench and Central and Western Sicily are the lowest (minimum M ≥ 6.5 recurrence times of 550–800 years). Most zones are probably capable of generating earthquakes up to magnitudes 7–7.5, with the exception of Central and Western Sicily where maximum events sizes most likely do not exceed 7.  相似文献   

11.
We conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for Turkey and the adjacent areas, applying the maximum likelihood method. The procedure allows for the use of either historical or instrumental data, or even a combination of the two. By using this method, we can estimate the earthquake hazard parameters, which include the maximum regional magnitude Mˆmax, the activity rate of seismic events and the well-known bˆ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. These three parameters are determined simultaneously using an iterative scheme. The uncertainty in the determination of the magnitudes was also taken into consideration. The return periods (RP) of earthquakes with a magnitude M ≥ m are also evaluated. The whole examined area is divided into 24 seismic regions based on their seismotectonic regime. The homogeneity of the magnitudes is an essential factor in such studies. In order to achieve homogeneity of the magnitudes, formulas that convert any magnitude to an MS-surface scale are developed. New completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions. Each of the obtained parameters is distributed into its respective seismic region, allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map. The earthquake hazard level is also calculated as a function of the form Θ = (Mˆmax,RP6.0), and a relative hazard scale (defined as the index K) is defined for each seismic region. The investigated regions are then classified into five groups using these parameters. This classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity. An attempt is then made to relate these values to the local tectonics.  相似文献   

12.
The seismically active Northwest (NW) Himalaya falls within Seismic Zone IV and V of the hazard zonation map of India. The region has suffered several moderate (~25), large-to-great earthquakes (~4) since Assam earthquake of 1897. In view of the major advancement made in understanding the seismicity and seismotectonics of this region during the last two decades, an updated probabilistic seismic hazard map of NW Himalaya and its adjoining areas covering 28–34°N and 74–82°E is prepared. The northwest Himalaya and its adjoining area is divided into nineteen different seismogenic source zones; and two different region-specific attenuation relationships have been used for seismic hazard assessment. The peak ground acceleration (PGA) estimated for 10% probability of exceedance in 50 and 10 years at locations defined in the grid of 0.25 × 0.25°. The computed seismic hazard map reveals longitudinal variation in hazard level along the NW Himalayan arc. The high hazard potential zones are centred around Kashmir region (0.70 g/0.35 g), Kangra region (0.50 g/0.020 g), Kaurik-Spitti region (0.45 g/0.20 g), Garhwal region (0.50 g/0.20 g) and Darchula region (0.50 g/0.20 g) with intervening low hazard area of the order of 0.25 g/0.02 g for 10% probability in 50 and 10 years in each region respectively.  相似文献   

13.
Clues to the understanding of intra- and inter-plate variations in strength or stress state of the crust can be achieved through different lines of evidence and their mutual relationships. Among these parameters Bouguer gravity anomalies and seismic b-values have been widely accepted over several decades for evaluating the crustal character and stress regime. The present study attempts a multivariate analysis for the Shillong Plateau using the Bouguer gravity anomaly and the earthquake database, and establishes a causal relationship between these parameters. Four seismic zones (Zones I–IV), with widely varying b-values, are delineated and an excellent correlation between the seismic b-value and the Bouguer gravity anomaly has been established for the plateau. Low b-values characterize the southwestern part (Zone IV) and a zone (Zone III) of intermediate b-values separates the eastern and western parts of the plateau (Zones I and II) which have high b-values. Positive Bouguer anomaly values as high as +40 mgal, a steep gradient in the Bouguer anomaly map and low b-values in the southwestern part of the plateau are interpreted as indicating a thinner crustal root, uplifted Moho and higher concentration of stress. In comparison, the negative Bouguer anomaly values, flat regional gradient in the Bouguer anomaly map and intermediate to high b-values in the northern part of the plateau are consistent with a comparatively thicker crustal root and lower concentration of stress, with intermittent dissipation of energy through earthquake shocks. Further, depth wise variation in the b-value for different seismic zones, delineated under this study, allowed an appreciation of intra-plateau variation in crustal thickness from ∼30 km in its southern part to ∼38 km in the northern part. The high b-values associated with the depth, coinciding with lower crust, indicate that the Shillong Plateau is supported by a strong lithosphere.  相似文献   

14.
Possible long-term seismic behaviour of the Northern strand of the North Anatolian Fault Zone, between western extreme of the 1999 İzmit rupture and the Aegean Sea, after 400 AD is studied by examining the historical seismicity, the submarine fault mapping and the paleoseismological studies of the recent scientific efforts. The long-term seismic behaviour is discussed through two possible seismicity models devised from M S ≥ 7.0 historical earthquakes. The estimated return period of years of the fault segments for M1 and M2 seismic models along with their standard deviations are as follows: F4 segment 255 ± 60 and 258 ± 12; F5 segment 258 ± 60 and 258 ± 53; F6 segment 258 ± 60 and 258 ± 53; F7 segment 286 ± 103 and 286 ± 90; F8 segment 286 ± 90 and 286 ± 36. As the latest ruptures on the submarine segments have been reported to be during the 1754–1766 earthquake sequence, and the 1912 mainshock rupture has been evidenced to extend almost all over the western part of the Sea of Marmara, our results imply imminent seismic hazard and, considering the mean recurrence time, a large earthquake to strike the eastern part of the Sea of Marmara in the next two decades.  相似文献   

15.
The main aim of the TOR project is to study the lithospheric–asthenospheric boundary structure under the Sorgenfrei–Tornquist Zone, across northern Germany, Denmark and southern Sweden. Relative arrival-time residuals of teleseismic P and S phases from 51 earthquakes, recorded by 150 seismic stations along the TOR array, were used to delineate the transition zone in the studied area. The effects of crustal structures were investigated by correcting the teleseismic residuals for travel-time variations in the crust based on a 3D crustal model derived from other data. The inversion was carried out for S phases. The results were then compared with the corresponding P-wave models. As expected, the derived models show that the relatively old and cold Baltic Shield has higher velocity at depth than the younger lithosphere farther South. The models show two sharp and distinct increases in depth to velocities which are low compared to our reference model, as we move from South to North. The location and sharpness of these boundaries suggests that the features resolved are, at least partially, compositional in origin, presumably related to mantle depletion. A sharp and steep subcrustal boundary is found roughly coincident with the southern edge of Sweden. This is below where the edge of the Baltic Shield is usually placed, based on surface geological evidence (the Sorgenfrei–Tornquist Zone). Another less significant transition is recognised more or less beneath the Elbe-lineament. Relatively high d(Vp / Vs) ratios under the central part of the profile (Denmark) indicate relatively low S-velocity in an area where a gravity high supports the hypothesis of extensive mafic intrusions.  相似文献   

16.
Earthquake hazard zonation of Sikkim Himalaya using a GIS platform   总被引：2，自引：1，他引：1  
An earthquake hazard zonation map of Sikkim Himalaya is prepared using eight thematic layers namely Geology (GE), Soil Site Class (SO), Slope (SL), Landslide (LS), Rock Outcrop (RO), Frequency–Wavenumber (F–K) simulated Peak Ground Acceleration (PGA), Predominant Frequency (PF), and Site Response (SR) at predominant frequencies using Geographic Information System (GIS). This necessitates a large scale seismicity analysis for seismic source zone classification and estimation of maximum earthquake magnitude or maximum credible earthquake to be used as a scenario earthquake for a deterministic or quasi-probabilistic seismic scenario generation. The International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) catalogues have been used in the present analysis. Combining b-value, fractal correlation dimension (Dc) of the epicenters and the underlying tectonic framework, four seismic source zones are classified in the northeast Indian region. Maximum Earthquake of M W 8.3 is estimated for the Eastern Himalayan Zone (EHZ) and is used to generate the seismic scenario of the region. The Geohazard map is obtained through the integration of the geological and geomorphological themes namely GE, SO, SL, LS, and RO following a pair-wise comparison in an Analytical Hierarchy Process (AHP). Detail analysis of SR at all the recording stations by receiver function technique is performed using 80 significant events recorded by the Sikkim Strong Motion Array (SSMA). The ground motion synthesis is performed using F–K integration and the corresponding PGA has been estimated using random vibration theory (RVT). Testing for earthquakes of magnitude greater than M W 5, a few cases presented here, establishes the efficacy and robustness of the F–K simulation algorithm. The geohazard coverage is overlaid and sequentially integrated with PGA, PF, and SR vector layers, in order to evolve the ultimate earthquake hazard microzonation coverage of the territory. Earthquake Hazard Index (EHI) quantitatively classifies the terrain into six hazard levels, while five classes could be identified following the Bureau of Indian Standards (BIS) PGA nomenclature for the seismic zonation of India. EHI is found to vary between 0.15 to 0.83 quantitatively classifying the terrain into six hazard levels as “Low” corresponding to BIS Zone II, “Moderate” corresponding to BIS Zone III, “Moderately High” belonging to BIS Zone IV, “High” corresponding to BIS Zone V(A), “Very High” and “Severe” with new BIS zones to Zone V(B) and V(C) respectively.  相似文献   

17.
The Maule, Chile, (Mw 8.8) earthquake on 27 February 2010 triggered deformation events over a broad area, allowing investigation of stress redistribution within the upper crust following a mega-thrust subduction event. We explore the role that the Maule earthquake may have played in triggering shallow earthquakes in northwestern Argentina and Chile. We investigate observed ground deformation associated with the Mw 6.2 (GCMT) Salta (1450 km from the Maule hypocenter, 9 h after the Maule earthquake), Mw 5.8 Catamarca (1400 km; nine days), Mw 5.1 Mendoza (350 km; between one to five days) earthquakes, as well as eight additional earthquakes without an observed geodetic signal. We use seismic and Interferometric Synthetic Aperture Radar (InSAR) observations to characterize earthquake location, magnitude and focal mechanism, and characterize how the non-stationary, spatially correlated noise present in the geodetic imagery affects the accuracy of our parameter estimates. The focal mechanisms for the far-field Salta and Catamarca earthquakes are broadly consistent with regional late Cenozoic fault kinematics. We infer that dynamic stresses due to the passage of seismic waves associated with the Maule earthquake likely brought the Salta and Catamarca regions closer to failure but that the involved faults may have already been at a relatively advanced stage of their seismic cycle. The near-field Mendoza earthquake geometry is consistent with triggering related to positive static Coulomb stress changes due to the Maule earthquake but is also aligned with the South America-Nazca shortening direction. None of the earthquakes considered in this study require that the Maule earthquake reactivated faults in a sense that is inconsistent with their long-term behavior.  相似文献   

18.
The central gap region of Himalaya, which lies in the northern part of the Indian subcontinent, is exposed to great seismic hazard. A three-dimensional attenuation structure (Q) of this region is obtained using the intensity data of four earthquakes (M 4.3–7.0) in the central Himalayan gap region and the damped least square inversion scheme. The technique is based on that given by Hashida and Shimazaki (J Phys Earth 32:299–316, 1984). The obtained Q structure explains the spatial distribution of isoseismals of the stronger earthquakes, which occurred in the recent past. The study area covers the Tehri town, which is the locale of one of the biggest earth fill dams of height 260 m. The spatial distribution of Q suggests that the Tehri town area is surrounded by lower Q medium, and hence any large earthquake in Tehri will pose great seismic hazard.  相似文献   

19.
The frequency–magnitude distributions of earthquakes are used in this study to estimate the earthquake hazard parameters for individual earthquake source zones within the Mainland Southeast Asia. For this purpose, 13 earthquake source zones are newly defined based on the most recent geological, tectonic, and seismicity data. A homogeneous and complete seismicity database covering the period from 1964 to 2010 is prepared for this region and then used for the estimation of the constants, a and b, of the frequency–magnitude distributions. These constants are then applied to evaluate the most probable largest magnitude, the mean return period, and the probability of earthquake of different magnitudes in different time spans. The results clearly show that zones A, B, and E have the high probability for the earthquake occurrence comparing with the other seismic zones. All seismic source zones have 100 % probability that the earthquake with magnitude ≤6.0 generates in the next 25 years. For the Sagaing Fault Zone (zones C), the next Mw 7.2–7.5 earthquake may generate in this zone within the next two decades and should be aware of the prospective Mw 8.0 earthquake. Meanwhile, in Sumatra-Andaman Interplate (zone A), an earthquake with a magnitude of Mw 9.0 can possibly occur in every 50 years. Since an earthquake of magnitude Mw 9.0 was recorded in this region in 2004, there is a possibility of another Mw 9.0 earthquake within the next 50 years.  相似文献   

20.
Gupta H.K. and Singh V.P., 1982. Is Shillong region, northeast India, undergoing a dilatancy stage precursory to a large earthquake? In: A.L. Hales and Z. Suzuki (Editors), Earthquake Prediction. Tectonophysics, 85: 31–33.  相似文献   

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