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1.
Imtiyaz A. Parvez 《Natural Hazards》2007,40(2):397-412
The Bayesian extreme-value distribution of earthquake occurrences has been used to estimate the seismic hazard in 12 seismogenic
zones of the North-East Indian peninsula. The Bayesian approach has been used very efficiently to combine the prior information
on seismicity obtained from geological data with historical observations in many seismogenic zones of the world. The basic
parameters to obtain the prior estimate of seismicity are the seismic moment, slip rate, earthquake recurrence rate and magnitude.
These estimates are then updated in terms of Bayes’ theorem and historical evaluations of seismicity associated with each
zone. From the Bayesian analysis of extreme earthquake occurrences for North-East Indian peninsula, it is found that for T = 5 years, the probability of occurrences of magnitude (M
w = 5.0–5.5) is greater than 0.9 for all zones. For M
w = 6.0, four zones namely Z1 (Central Himalayas), Z5 (Indo-Burma border), Z7 (Burmese arc) and Z8 (Burma region) exhibit high
probabilities. Lower probability is shown by some zones namely␣Z4, Z12, and rest of the zones Z2, Z3, Z6, Z9, Z10 and Z11
show moderate probabilities. 相似文献
2.
Sandeep Gupta Nagaraju Kanna Sudesh Kumar K. Sivaram 《Journal of the Geological Society of India》2018,91(5):523-534
Seismic-potential for the Andaman Arc System (AAS) is evaluated using a three-tier approach: (i) the seismic b-values derived using a revised and homogenized earthquake catalog for Mw ≥ 4.7, with uniform Mw, for the period 1964–2013 created from ISC Data, (ii) Free-air gravity-anomalies for AAS and their geologic interpretation and (iii) deep crustal structure from seismic reflection surveys and 3D seismic tomography results. Both long-term spatial b-value anomalies for the period 1964-2013 and temporal b-value anomalies for a shorter period (2002–2013) have been estimated. The b-value maps are interpreted in terms of the stress regime acting across AAS and stressed asperities inferred along the strike of AAS. Eight distinguishable seismic-zones are identified and their seismic potential is examined by temporal bvalue anomalies in producing moderate to large earthquakes. The latter demonstrates ‘low-high’ or ‘high-low’ couplet over years, and that a variation in b-value more than 20% compared to the previous year value is likely to produce an earthquake event with Mw ≥ 6.0. Some support to this interpretation comes from the regional Free-air gravity-anomalies and deep crustal structure interpreted from hypocentral distribution of earthquakes. The high b-values are seemingly associated with magma chambers or low velocity crust; creating asperity zones due to multiple batholithic intrusions at plate boundary. This geologic interpretation is evidenced by 3D P-wave seismic tomography and velocity heterogeneity study for AAS reported by us elsewhere. 相似文献
3.
震级-频度分布（FMD）是地震学研究中最重要的经验公式之一,相关系数b是构造学和地震危险性评估的重要因子,具有表征前震和余震的特性。辽宁省地震多发生在金州断裂附近,自1975年海城7.3级地震发生后,与金州断裂交汇的海城河—大洋河断裂开启活跃模式,其东南端岫岩附近在1999年又发生5.6级地震。近年来盖州附近地震活动也在增强。因此,本文利用b值空间分布特征对海城及其邻区的应力分布特点进行研究。震源定位准确与否直接影响b值计算,双差定位后的数据与常规目录相比具有更高的精度,但是完整性有一定下降。本文收集了中国地震台网1981—2005年的辽宁省地震目录,并进行双差定位,比较分析了常规目录数据和双差数据的b值分布差异,认为在地震密集区,双差定位后的数据可以被用来获得更准确的b值。对主要研究区进行网格划分,使用双差数据,得到b值的水平和垂直分布特征。结果表明：b值为0.6~1.8,随深度增加而降低;岫岩和盖州震区具有较低的b值,意味着具有较高的地震危险性;浑河震区与海城河—大洋河断裂东南方向具有较高的b值,说明该区域未来发生大地震的概率很低;与金州断裂交汇区域的b值在1.0附近,说明该地区应力暂时处于稳定状态,未来具有较低的地震危险性。 相似文献
4.
We compiled available information of damages and other effects caused by the September 18, 2011, Sikkim–Nepal border earthquake from the print and electronic media, and interpreted them to obtain Modified Mercalli Intensity (MMI) at over 142 locations. These values are used to prepare the intensity map of the Sikkim earthquake. The map reveals several interesting features. Within the meizoseismal area, the most heavily damaged villages are concentrated toward the eastern edge of the inferred fault, consistent with eastern directivity. The intensities are amplified significantly in areas located along rivers, within deltas or on coastal alluvium such as mud flats and salt pans. We have also derived empirical relation between MMI and ground motion parameters using least square regression technique and compared it with the available relationships available for other regions of the world. Further, seismic intensity information available for historical earthquakes which have occurred in NE Himalayas along with present intensity has been utilized for developing attenuation relationship for NE India using two-step regression analyses. The derived attenuation relation is useful for assessing damage of a potential future earthquake (earthquake scenario-based planning purposes) for the northeast Himalaya region.
相似文献5.
H. N. Srivastava B. K. Bansal Mithila Verma 《Journal of the Geological Society of India》2013,82(1):15-22
The largest earthquake (Mw 8.4 to 8.6) in Himalaya reported so far occurred in Assam syntaxial bend in 1950. However, some recent studies have suggested for earthquake of magnitude Mw 9 or more in the Himalayan region. In this paper, we present a detailed analysis of seismological data extending back to 1200 AD, and show that earthquake in Himalayan region may not be expected to be as large as those of subduction zones. Also, there appears to be a lateral variation in the earthquake magnitude, being lesser in the western syntaxial bend when compared close to the eastern syntaxial bend. This is attributed to the difference in the plate boundary scenario; dominance of strike-slip and thrusting along the western syntaxis as against thrusting and remnant subduction along the eastern syntaxis. 相似文献
6.
东南亚地区是“21世纪海上丝绸之路”（以下简称“海洋丝路”）的重要组成部分,该区历史上曾发生十余次巨大地震,地震及其次生地质灾害是威胁东南亚地区经济社会发展和国际合作的主要自然灾害。系统梳理该区地震活动的时空分布特征及评估未来灾害风险格局,对于推进“一带一路”倡议实施及区域经济社会可持续发展具有重要意义。文章基于东南亚地区1900年以来M≥5地震的时空分布统计分析和地震b值计算,揭示出该区的地震活动在时间上表现出活跃期与平静期交替变化的特征;空间上表现出明显的聚集效应,成丛性强且主要集中在5个地震统计区内,其中印尼—马来多岛弧盆系地震区和菲律宾群岛地震区的地震活动最为活跃。总体而言,东南亚5个地震区的b值偏低,在0.42~0.91之间。该区内的地震b值也存在时空差异,受大地震事件、俯冲带年龄、活动断裂带和震源深度等众多因素影响,但主控因素在不同区域有所不同。地震b值时空变化特征对区域地震活动预测具有启示作用。上述认识为推进“海洋丝路”工程建设和“一带一路”防灾减灾对策提供了科学支撑。 相似文献
7.
8.
An earthquake is a natural phenomenon which is very frequent in Himalayan region in India. In southern peninsula India, the spatial occurrence of earthquake is irregular, whereas the northeastern, the north and the northwestern Himalayan parts of India are subjected to regular occurrences of earthquakes as they mark the boundary of the Eurasian and the Indian Plate. Hence, it is important to study and develop spatial model and information tool to understand the seismic phenomenon. The geoinformatic technique plays a significant role in the analysis of geodatabase to study the natural disaster and hazard assessment. The main aim of the present study is to develop geospatial model based on earthquake hazard assessment tool (EaHaAsTo) through integrated geological and geoinformatic techniques to better understand the earthquake occurrences zones. The spatial and non-spatial data were collected and integrated in a GIS to prepare geospatial databases. The thematic and quantitative databases were generated, and analysis was carried out to understand the seismic characteristics of the study area. The geospatial model was developed by integrating thematic databases and geospatial analyzed using weighted linear combination method. Finally, the GIS based on customized EaHaAsTo was developed to visualize the output of the model in qualitative and quantitative forms. 相似文献
9.
We present a mineral systems approach to predictive mapping of orogenic gold prospectivity in the Giyani greenstone belt (GGB) by using layers of spatial evidence representing district-scale processes that are critical to orogenic gold mineralization, namely (a) source of metals/fluids, (b) active pathways, (c) drivers of fluid flow and (d) metal deposition. To demonstrate that the quality of a predictive map of mineral prospectivity is a function of the quality of the maps used as sources of spatial evidence, we created two sets of prospectivity maps — one using an old lithologic map and another using an updated lithological map as two separate sources of spatial evidence for source of metals/fluids, drivers of fluid flow and metal deposition. We also demonstrate the importance of using spatially-coherent (or geologically-consistent) deposit occurrences in data-driven predictive mapping of mineral prospectivity. The best predictive orogenic gold prospectivity map obtained in this study is the one that made use of spatial evidence from the updated lithological map and spatially-coherent orogenic gold occurrences. This map predicts 20% of the GGB to be prospective for orogenic gold, with 89% goodness-of-fit between spatially-coherent inactive orogenic gold mines and individual layers of spatial evidence and 89% prediction-rate against spatially-coherent orogenic gold prospects. In comparison, the predictive gold prospectivity map obtained by using spatial evidence from the old lithological map and all gold occurrences has 80% goodness-of-fit but only 63% prediction-rate. These results mean that the prospectivity map based on spatially-coherent gold occurrences and spatial evidence from the updated lithological map predicts exploration targets better (i.e., 28% smaller prospective areas with 9% stronger fit to training gold mines and 26% higher prediction-rate with respect to validation gold prospects) than the prospectivity map based on all known gold occurrences and spatial evidence from the old lithological map. 相似文献
10.
This study presents the future seismic hazard map of Coimbatore city, India, by considering rupture phenomenon. Seismotectonic
map for Coimbatore has been generated using past earthquakes and seismic sources within 300 km radius around the city. The
region experienced a largest earthquake of moment magnitude 6.3 in 1900. Available earthquakes are divided into two categories:
one includes events having moment magnitude of 5.0 and above, i.e., damaging earthquakes in the region and the other includes
the remaining, i.e., minor earthquakes. Subsurface rupture character of the region has been established by considering the
damaging earthquakes and total length of seismic source. Magnitudes of each source are estimated by assuming the subsurface
rupture length in terms of percentage of total length of sources and matched with reported earthquake. Estimated magnitudes
match well with the reported earthquakes for a RLD of 5.2% of the total length of source. Zone of influence circles is also
marked in the seismotectonic map by considering subsurface rupture length of fault associated with these earthquakes. As earthquakes
relive strain energy that builds up on faults, it is assumed that all the earthquakes close to damaging earthquake have released
the entire strain energy and it would take some time for the rebuilding of strain energy to cause a similar earthquake in
the same location/fault. Area free from influence circles has potential for future earthquake, if there is seismogenic source
and minor earthquake in the last 20 years. Based on this rupture phenomenon, eight probable locations have been identified
and these locations might have the potential for the future earthquakes. Characteristic earthquake moment magnitude (M
w
) of 6.4 is estimated for the seismic study area considering seismic sources close to probable zones and 15% increased regional
rupture character. The city is divided into several grid points at spacing of 0.01° and the peak ground acceleration (PGA)
due to each probable earthquake is calculated at every grid point in city by using the regional attenuation model. The maximum
of all these eight PGAs is taken for each grid point and the final PGA map is arrived. This map is compared to the PGA map
developed based on the conventional deterministic seismic hazard analysis (DSHA) approach. The probable future rupture earthquakes
gave less PGA than that of DSHA approach. The occurrence of any earthquake may be expected in near future in these eight zones,
as these eight places have been experiencing minor earthquakes and are located in well-defined seismogenic sources. 相似文献
11.
The slow spreading mid-Indian Ocean ridge system containing the Carlsberg, Central and Southwest Indian ridges is seismically
very active. In the present study, a detailed analysis has been carried out of the data of earthquake sources along different
ridge segments in order to investigate the spatial and temporal clustering patterns and to evaluate crustal processes related
to the swarm occurrences along these ridges. The spatial and temporal clustering pattern of the recent earthquakes (1980–1990)
pertaining to nine major spreading segments and eight fracture zones suggests that the events cluster in greater proportion
along the spreading segments than along the fracture zones.
We performed a systematic search of earthquake catalogue during the period 1964–1990 by examining the spatio-temporal hypocentral
clusters in order to identify the swarm occurrences along these ridges. The search included eighteen prominent sequences,
of which, thirteen were earthquake swarms. Except two, all other swarms were found to be occurring mainly on the spreading
segments. The maximum magnitude observed in these swarms is mb = 5.4 and have many events predominantly showing normal faulting mechanisms. The spatial disposition and temporal activity
of the events in swarms is much similar to the foreshock-mainshock-aftershock sequences observed along the spreading rift
valley zones. These characteristics help us to support that swarms along the slow spreading mid-Indian Ocean ridges are the
result of extensional tectonic activity, leading to the development of the median valley topography, a mechanism similar to
that proposed by Bergman and Solomon (1990) for the Mid-Atlantic Ridge. 相似文献
12.
This paper examines the variability of seismic activity observed in the case of different geological zones of peninsular India (10°N–26°N; 68°E–90°E) based on earthquake catalog between the period 1842 and 2002 and estimates earthquake hazard for the region. With compilation of earthquake catalog in terms of moment magnitude and establishing broad completeness criteria, we derive the seismicity parameters for each geologic zone of peninsular India using maximum likelihood procedure. The estimated parameters provide the basis for understanding the historical seismicity associated with different geological zones of peninsular India and also provide important inputs for future seismic hazard estimation studies in the region. Based on present investigation, it is clear that earthquake recurrence activity in various geologic zones of peninsular India is distinct and varies considerably between its cratonic and rifting zones. The study identifies the likely hazards due to the possibility of moderate to large earthquakes in peninsular India and also presents the influence of spatial rate variation in the seismic activity of this region. This paper presents the influence of source zone characterization and recurrence rate variation pattern on the maximum earthquake magnitude estimation. The results presented in the paper provide a useful basis for probabilistic seismic hazard studies and microzonation studies in peninsular India. 相似文献
13.
Seismic intensity information of historical earthquake of NW Himalayas has been utilized for evaluating the attenuation of
the intensity with the epicentral distance. Purposefully, the observed intensity of big historical earthquake may implicitly
incorporate some site effects arising due to the near surface geology or deposited soil. The isoseismal map of the 1905 Kangra
earthquake yields an area of perceptibility defined by the intensity VII (RF Scale), which is mainly elongated in the NNW-SSE
direction. However, the higher isoseismals of intensity VIII and IX are more symmetrical and elongated in the SE direction.
These isoseismals are more compressed in the northeast and northwest direction indicating fast attenuation characteristics,
which may be either due to the presence of any transverse geotectonic feature or change in lithology. In the present study
the regression relation has been derived to incorporate the attenuation of intensity with variable magnitudes at different
epicentral distances. The derived attenuation relation is useful for assessing damage of a potential future earthquake (earthquake
scenario-based planning purposes) for the Kangra region, Northwest Himalaya. The derived relation is mentioned below:
|
I(R,Ms) = 2.856 + 1.31*Ms - 0.0017 * R - 0.9598*ln(R)I(R,Ms) = 2.856 + 1.31*Ms - 0.0017 * R - 0.9598*\ln (R) 相似文献
14.
Sequential cumulative moment release data of macroearthquakes (Mw≥4.3) of seventeen seismic zones (A to Q) belonging to NE-Himalaya, Burmese-Andaman arc and West- Sunda arc are analysed by Hurst analysis, a non-parametric statistical procedure to identify clustering of low and high values in a time series. The moment release in a zone occurs in alternate positive, negative and positive sloping segments forming a wave like pattern with intervening small horizontal segment. The negative sloping segments indicate decelerated moment release pattern or temporal slackening of elastic strain release with high b–value (>0.95). The horizontal segment indicates temporal clustering of moderate magnitude events/seismic moments with moderate b-values (0.8–0.95). The positive segment is characterised by accelerated moment release within a short span of time indicating temporal clustering of larger magnitude earthquakes/seismic moments and exhibit lowest b–value (<0.7). All zones attest moderate to high Hurst K values, range 0.7-0.86. The pattern in Hurst plots, specially a reversal of trend after prolong negative slope is used for earthquake prognostication in the seismic zones. Our analysis shows that most of the zones register a notable reversal of Hurst clustering trend after a prolonged negative slope which is accompanied by a major earthquake near its end. However, South Burma region (Zone-I) and Tripura fold belt and Bangladesh Plain (Zone-K) do not show any moderate or large shock around the end of the negative sloping trend in Hurst plot. Hence, these two zones can be considered more prone to produce moderate to larger earthquakes in future. 相似文献
15.
BassamFAIBassam 《中国地质大学学报(英文版)》2003,14(3):283-292
Gengma region, Sanjiang district is known to have some large-scale gold deposits. GIS predictive model for hydroghermal gold potential was carried out in this region using weights of evidence modeling technique. Datasets used include large-scale hydroghermal gold deposit records, geological, geophysical and remote sensing imagery. Based on the geological and mineral characteristics of areas with known gold occurrences in Sanjiang, several geological features were thought to be indicative of areas with potential for the occurrence of hydroghtermal gold deposits. Indicative features were extracted from geoexploration datasets for use as input in the predictive model. The features include host rock lithology, geologic structures, wallrock alteration and associated (volcanic-plutonic) igneous rocks. To determine which of the indicative geological features are important spatial predictors of area with potential for gold deposits, spatial analysis was done through the modeling method. The input maps were buffered and the optimum distance of spatial association for each geological feature was determined by calculating the contrast and studentized contrast. Five feature maps were converted to binary predictor patterns and used as evidential layers for predictive modeling. The binary patterns were integrated in two combinations, each of which consists of four patterns in order to avoid over prediction due to the effect of duplicate features in the two structural evidences. The two produced potential maps define almost similar favorable zones. Areas of intersections between these zones in the two potential maps placed the highest predictive favorable zones in the region. 相似文献
16.
Seismic hazard in mega city Kolkata, India 总被引：2，自引：1，他引：1
The damages caused by recent earthquakes in India have been a wake up call for people to take proper mitigation measures,
especially the major cities that lie in the high seismic hazard zones. Kolkata City, with thick sediment deposit (∼12 km),
one of the earliest cities of India, is an area of great concern as it lies over the Bengal Basin and lies at the boundary
of the seismic zones III and IV of the zonation map of India. Kolkata has been affected by the 1897 Shillong earthquake, the
1906 Calcutta earthquake, and the 1964 Calcutta earthquake. An analysis on the maximum magnitude and b-value for Kolkata City region is carried out after the preparation of earthquake catalog from various sources. Based on the
tectonic set-up and seismicity of the region, five seismic zones are delineated, which can pose a threat to Kolkata in the
event of an earthquake. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3:
Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ), and Zone 5: Shield Zone (SZ). The maximum magnitude (m
max) for Zones 1, 2, 3, 4, and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. A probability
of 10% exceedance value in 50 years is used for each zone. The probabilities of occurrences of earthquakes of different magnitudes
for return periods of 50 and 100 years are computed for the five seismic zones. The Peak Ground Acceleration (PGA) obtained
for Kolkata City varies from 0.34 to 0.10 g. 相似文献
17.
The increased socio-economic significance of landslides has resulted in the application of statistical methods to assess their
hazard, particularly at medium scales. These models evaluate where, when and what size landslides are expected. The method presented in this study evaluates the landslide hazard on the basis of homogenous susceptible
units (HSU). HSU are derived from a landslide susceptibility map that is a combination of landslide occurrences and geo-environmental
factors, using an automated segmentation procedure. To divide the landslide susceptibility map into HSU, we apply a region-growing
segmentation algorithm that results in segments with statistically independent spatial probability values. Independence is
tested using Moran’s I and a weighted variance method. For each HSU, we obtain the landslide frequency from the multi-temporal data. Temporal and
size probabilities are calculated using a Poisson model and an inverse-gamma model, respectively. The methodology is tested
in a landslide-prone national highway corridor in the northern Himalayas, India. Our study demonstrates that HSU can replace
the commonly used terrain mapping units for combining three probabilities for landslide hazard assessment. A quantitative
estimate of landslide hazard is obtained as a joint probability of landslide size, of landslide temporal occurrence for each
HSU for different time periods and for different sizes. 相似文献
18.
Tapas R. Martha Priyom Roy Ritwik Mazumdar K. Babu Govindharaj K. Vinod Kumar 《Landslides》2017,14(2):697-704
High magnitude earthquakes trigger numerous landslides and their occurrences are mainly controlled by terrain parameters. We created an inventory of 15,551 landslides with a total area of 90.2 km2 triggered by the 2015 Mw 7.8 (Gorkha) and Mw 7.3 (Dolakha) earthquakes in Nepal, through interpretation of very high resolution satellite images (e.g. WorldView, Pleiades, Cartosat-1 and 2, Resourcesat-2). Our spatial analysis of landslide occurrences with ground acceleration, slope, lithology and surface defomation indicated ubiquitous control of steep slope on landslides with ground acceleration as the trigger. Spatial distribution of landslides shows increasing frequency away from the Gorkha earthquake epicentre up to 130 km towards east, dropping sharply thereafter, which is an abnormal phenomenon of coseismic landslides. Landslides are laterally concentrated in three zones which matches well with the seismic rupture evolution of Gorkha earthquake, as reported through teleseismic measurements. 相似文献
19.
We estimate the energetic and spatial characteristics of seismicity in the Algeria–Morocco region using a variety of seismic and statistical parameters, as a first step in a detailed investigation of regional seismic hazard. We divide the region into five seismotectonic regions, comprising the most important tectonic domains in the studied area: the Moroccan Meseta, the Rif, the Tell, the High Plateau, and the Atlas. Characteristic seismic hazard parameters, including the Gutenberg–Richter b-value, mean seismic activity rate, and maximum possible earthquake magnitude, were computed using an extension of the Aki–Utsu procedure for incomplete earthquake catalogs for each domain, based on recent earthquake catalogs compiled for northern Morocco and northern Algeria. Gutenberg–Richter b-values for each zone were initially estimated using the approach of Weichert (Bull Seismol Soc Am 70:1337–1346, 1980): the estimated b-values are 1.04 ± 0.04, 0.93 ± 0.10, 0.72 ± 0.03, 0.87 ± 0.02, and 0.77 ± 0.02 for the Atlas, Meseta, High Plateau, Rif, and Tell seismogenic zones, respectively. The fractal dimension D 2 was also estimated for each zone. From the ratio D 2/b, it appears that the Tell and Rif zones, with ratios of 2.09 and 2.12, respectively, have the highest potential earthquake hazard in the region. The Gutenberg–Richter relationship analysis allows us to derive that in the Tell and Rif, the number of earthquake with magnitude above Mw 4.0, since 1925 normalized to decade and to square cell with 100-km sides is equal to 2.6 and 1.91, respectively. This study provides the first detailed information about the potential seismicity of these large domains, including maximum regional magnitudes, characteristics of spatial clustering, and distribution of seismic energy release. 相似文献20.
Earthquake Modelling at the Country Level Using Aggregated Spatio-Temporal Point Processes 总被引：1，自引：1，他引：0
The goal of this paper is to derive a hazard map for earthquake occurrences in Pakistan from a catalogue that contains spatial coordinates of shallow earthquakes of magnitude 4.5 or larger aggregated over calendar years. We test relative temporal stationarity by the KPSS statistic and use the inhomogeneous J-function to test for inter-point interactions. We then formulate a cluster model, and de-convolve in order to calculate the hazard map, and verify that no particular year has an undue influence on the map. Within the borders of the single country, the KPSS test did not show any deviation from homogeneity in the spatial intensities. The inhomogeneous J-function indicated clustering that could not be attributed to inhomogeneity, and the analysis of aftershocks showed some evidence of two major shocks instead of one during the 2005 Kashmir earthquake disaster. Thus, the spatial point pattern analysis carried out for these data was insightful in various aspects and the hazard map that was obtained may lead to improved measures to protect the population against the disastrous effects of earthquakes. 相似文献
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