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1.
The Himalayan fold-thrust belt has been visited by many disastrous earthquakes (magnitude > 6) time and again. This active collisional orogen bordering Indian subcontinent in the north remains a potential seismic threat of similar magnitude in the adjoining countries like India, Pakistan, Nepal, Bhutan and China. Though earthquake forecasting is riddled with all conjectures and still not a proven presumption, identifying likely source zones of such disastrous earthquakes would be an important contribution to seismic hazard assessment. In this study, we have worked out spatio-temporal clustering of earthquakes (Mb ?? 4.5; 1964?C2006) in the Himalayas. ??Point density?? spatial statistics has helped in detecting 22 spatial seismicity clusters. Earthquake catalog is then treated with a moving time-distance window technique (inter-event time 35 days and distance 100 ± 20 km) to bring out temporal clusters by recognizing several foreshock-main shock-aftershock (FMA) sequences. A total of 53 such temporal sequences identified in the process are confined within the 22 spatial clusters. Though each of these spatio-temporal clusters deserves in-depth analysis, we short-listed only eight such clusters that are dissected by active tectonic discontinuities like MBT/MCT for detail study. Spatio-temporal clusters have been used to constrain the potential source zones. These eight well-defined spatio-temporal clusters demonstrate recurrent moderate to large earthquakes. We assumed that the length of these clusters are indicating the possible maximum rupture lengths and thus empirically estimated the maximum possible magnitudes of eight clusters that can be generated from them (from west to east) as 8.0, 8.3, 8.2, 8.3, 8.2, 8.4, 8.0 and 7.7. Based on comparative study of the eight cluster zones contemplating with their temporal recurrences, historical seismic records, presence of intersecting faults and estimated magnitudes, we have guessed the possibility that Kangra, East Nepal, Garhwal and Kumaun?CWest Nepal clusters, in decreasing order of earthquake threat, are potential source zones for large earthquakes (??7.7 M) in future. 相似文献
2.
Iranian strong motion records as well as detailed conditions of their instrument sites and the characteristics of their causative seismic sources are compiled and processed. The dataset consists of 2286 three-component records from 461 Iranian earthquakes with at least two high-quality records having moment magnitude from 3.9 to 7.3. These records are about 20% of the Iranian database and are suitable for seismic hazard analysis and engineering applications. Perhaps for the first time in the literature, the distance to the surface projection of the fault is reported for a great number of records corresponding to earthquakes with M > 6.0. The raw accelerations are processed using the wavelet de-noising method. Having corrected and filtered these raw data, the pseudospectral accelerations are calculated for each of the three components of time series, separately. In addition to the ground motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record is also developed. Moreover, careful revision of the characteristics of the earthquakes such as location, magnitude, style of faulting and fault rupture plane geometry, if available, is carried out using the best available information in a scientifically sound manner. Finally, we also focus on special ground motion records including records with peak ground acceleration (PGA) >300 cm/s2 and distances less than 30 km. These are “exceptional” records in the Iranian dataset and include less than 2% of the selected dataset. 相似文献
3.
Jyh-Woei Lin 《Arabian Journal of Geosciences》2011,4(3-4):575-593
The goal of this research is to examine one-dimensional total electron content (TEC) data using principal component analysis (PCA) to search for total electron content (TEC) anomalies associated with large earthquakes in 24 h prior to nucleation. The characteristics of principal eigenvalues generated for TEC prior to 24 earthquakes of magnitude scale M?≥?5.0 and 6 lesser earthquakes of magnitude scale M?<?5 that occurred in Taiwan from 01 January 2000 to 31 December 2001 are examined. In an earlier paper, I was able to confirm the statistical findings of Liu et al. (J Geophys Res 111, 2006) that sparse earthquake-associated TEC anomalies existed in 5 days prior to the 12 large earthquakes they examined (Lin, Terr Atm Ocean Sci, 2010). In this paper, I wish to examine the subtlety of principal component analysis in detecting earthquake-associated TEC anomalies by examining if such precursors can be detected in 24 h prior to large earthquakes. Of the earthquakes examined, TEC anomalies given by clear extreme principal eigenvalues were evident within 24 h of nucleation for 21 of the 24 earthquakes of M?≥?5.0. After making allowance for the general status of background TEC, it is clear that these extreme principal eigenvalues are representative of earthquake-associated anomalies. For the smaller earthquakes (M?<?5), it was not possible to differentiate earthquake-associated anomalies from background effects on TEC status. These new findings confirm the validity of PCA in searching for earthquake-associated TEC anomalies and show that it is subtle enough to detect TEC anomalies within 24 h leading to a large earthquake. If this approach continues to prove successful, it could theoretically be used in real-time prediction of large earthquakes through early detection of earthquake-associated TEC anomalies. 相似文献
4.
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
5.
Since the year 1973, more than 54,000 M w ≥ 3.0 earthquakes have occurred around Taiwan, and their magnitude–frequency relationship was found following with the Gutenberg–Richter recurrence law with b value equal to 0.923 from the least-square calculation. However, using this b value with the McGuire–Arabasz algorithm results in some disagreement between observations and expectations in magnitude probability. This study introduces a simple approach to optimize the b value for better modeling of the magnitude probability, and its effectiveness is demonstrated in this paper. The result shows that the optimal b value can better model the observed magnitude distribution, compared with two customary methods. For example, given magnitude threshold = 5.0 and maximum magnitude = 8.0, the optimal b value of 0.835 is better than 0.923 from the least-square calculation and 0.913 from maximum likelihood estimation for simulating the earthquake’s magnitude probability distribution around Taiwan. 相似文献
6.
Earthquakes in Kenya are common along the Kenya Rift Valley because of the slow divergent movement of the rift and hydrothermal processes in the geothermal fields. This implies slow but continuous radiation of seismic energy, which relieves stress in the subsurface rocks. On the contrary, the NW-SE trending rift/fault zones such as the Aswa-Nyangia fault zone and the Muglad-Anza-Lamu rift zone are the likely sites of major earthquakes in Kenya and the East African region. These rift/fault zones have been the sites of a number of strong earthquakes in the past such as the M w = 7.2 southern Sudan earthquake of 20 May 1990 and aftershocks of M w = 6.5 and 7.1 on 24 May 1990, the 1937 M s = 6.1 earthquake north of Lake Turkana close to the Kenya-Ethiopian border, and the 1913 M s = 6.0 Turkana earthquake, among others. Source parameters of the 20 May 1990 southern Sudan earthquake show that this earthquake consists of only one event on a fault having strike, dip, and rake of 315°, 84°, and ?3°. The fault plane is characterized by a left-lateral strike slip fault mechanism. The focal depth for this earthquake is 12.1 km, seismic moment M o = 7.65 × 1019 Nm, and moment magnitude, M w = 7.19 (?7.2). The fault rupture started 15 s earlier and lasted for 17 s along a fault plane having dimensions of ?60 km × 40 km. The average fault dislocation is 1.1 m, and the stress drop, ?σ, is 1.63 MPa. The distribution of historical earthquakes (M w ≥ 5) from southern Sudan through central Kenya generally shows a NW-SE alignment of epicenters. On a local scale in Kenya, the NW–SE alignment of epicenters is characterized by earthquakes of local magnitude M l ≤ 4.0, except the 1928 Subukia earthquake (M s = 6.9) in central Kenya. This NW–SE alignment of epicenters is consistent with the trend of the Aswa-Nyangia Fault Zone, from southern Sudan through central Kenya and further southwards into the Indian Ocean. We therefore conclude that the NW–SE trending rift/fault zones are sites of strong earthquakes likely to pose the greatest earthquake hazard in Kenya and the East African region in general. 相似文献
7.
针对2015年4月25日尼泊尔M8.1地震后喜马拉雅造山带的未来地震危险性问题,通过对喜马拉雅带历史大地震应变能释放和在尼泊尔地震发震前后的区域地震活动图像进行了分析研究。结果发现喜马拉雅带很可能已进入新-轮的地震活跃期。此次尼泊尔大地震不足以将喜马拉雅带中段的地壳应变能全部释放,喜马拉雅带中段的地震活动和藏南裂谷带地震活动具有密切的关联,在喜马拉雅带中段和藏南裂谷带还将有大地震活动。同时研究结果还显示现今在喜马拉雅带的东段存在阿萨姆围空区和不丹围空区,在喜马拉雅的西段出现噶尔围空区,喜马拉雅西段新德里和西藏接壤地区以及喀喇昆仑断裂上噶尔县地区地震危险性很高,喜马拉雅东段林芝山南地区以南的阿萨姆和不丹地区危险性很高,应引起重视。 相似文献
8.
A shallow-focus damaging earthquake of magnitude 6.9?Mw struck the Sikkim Himalaya, north-east India, on 18 September 2011 at 12:40:48 UTC (06:10:48PM IST). The epicentre was located north-west of Chungthang on Indo-Nepal border of Sikkim Himalaya. The earthquake was widely felt in northern India and caused widespread damage to poorly built and framed structures in Sikkim region, northern Bihar, eastern Nepal, southern Bhutan and part of Tibet adjoining Sikkim Himalaya. A lot of secondary effects in the form of landslides, rockfalls and landslide lake outburst flood were caused due to strong shaking effect of the earthquake. Maximum intensity IX according to the European Macroseismic Scale-98 was observed in the meizoseismal zone surrounding Chungthang village. Asymmetrical distribution and heterogeneous damage pattern demonstrate intensity attenuation characteristics of the region. Although the regional tectonic framework of Sikkim region indicates compressional thrust tectonics regime, according to CMT fault-plane solution this earthquake involved predominantly strike-slip motion on a steep fault. Unlike Nepal and north-west Himalaya where microseismicity and large earthquakes indicate thrust mechanism, this Sikkim earthquake suggests that strike-slip principal component may imply transcurrent deformation. 相似文献
9.
In this work, we consider historical earthquakes registered in Chile (from 1900 up to 2010) with epicenters located between 19 and 40°S latitude, in order to evaluate the probabilities of the occurrence of strong earthquakes along Chile in the near future. Applying Gumbel??s technique of first asymptotic distribution, Wemelsfelder??s theory and Gutenberg?CRichter relationship, we estimate that during the next decade strong earthquakes with Richter magnitudes larger than 8.7?C8.9 could occur along Chile. According to our analysis, probabilities for the occurrence of such a strong earthquake range between 64 and 46% respectively. Particularly in the very well known ??seismic gap?? of Arica, a convergence motion between Nazca and South American plates of 77?C78?mm/year represents more than 10?m of displacement accumulated since the last big interplate subduction earthquake in this area over 134?years ago. Therefore, this area already has the potential for an earthquake of magnitude >8. 相似文献
10.
The Himalayas are one of very active seismic regions in the world where devastating earthquakes of 1803 Bihar–Nepal, 1897 Shillong, 1905 Kangra, 1934 Bihar–Nepal, 1950 Assam and 2011 Sikkim were reported. Several researchers highlighted central seismic gap based on the stress accumulation in central part of Himalaya and the non-occurrence of earthquake between 1905 Kangra and 1934 Bihar–Nepal. The region has potential of producing great seismic event in the near future. As a result of this seismic gap, all regions which fall adjacent to the active Himalayan region are under high possible seismic hazard due to future earthquakes in the Himalayan region. In this study, the study area of the Lucknow urban centre which lies within 350 km from the central seismic gap has been considered for detailed assessment of seismic hazard. The city of Lucknow also lies close to Lucknow–Faizabad fault having a seismic gap of 350 years. Considering the possible seismic gap in the Himalayan region and also the seismic gap in Lucknow–Faizabad fault, the seismic hazard of Lucknow has been studied based on deterministic and the probabilistic seismic hazard analysis. Results obtained show that the northern and western parts of Lucknow are found to have a peak ground acceleration of 0.11–0.13 g, which is 1.6- to 2.0-fold higher than the seismic hazard compared to the other parts of Lucknow. 相似文献
11.
Amrita Yadav D. Shashidhar K. Mallika N. Purnachandra Rao Sunil Rohilla H. V. S. Satyanarayana D. Srinagesh Harsh Gupta 《Natural Hazards》2013,69(1):965-979
New empirical relations are derived for source parameters of the Koyna–Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range M L 3.5–5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 1013–1016 Nm, 0.1–0.4 km, 2.9–9.4 Hz and 3–26 MPa, respectively. Linear relationships are obtained among the seismic moment (M 0), local magnitude (M L), moment magnitude (M w), corner frequency (fc) and stress drop (?σ). The stress drops in the Koyna–Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna–Warna region. 相似文献
12.
A. van Geen K. Radloff Z. Aziz Z. Cheng M.R. Huq K.M. Ahmed B. Weinman S. Goodbred H.B. Jung Y. Zheng M. Berg P.T.K. Trang L. Charlet J. Metral D. Tisserand S. Guillot S. Chakraborty A.P. Gajurel B.N. Upreti 《Applied Geochemistry》2008
One of the reasons the processes resulting in As release to groundwater in southern Asia remain poorly understood is the high degree of spatial variability of physical and chemical properties in shallow aquifers. In an attempt to overcome this difficulty, a simple device that collects groundwater and sediment as a slurry from precisely the same interval was developed in Bangladesh. Recently published results from Bangladesh and India relying on the needle-sampler are augmented here with new data from 37 intervals of grey aquifer material of likely Holocene age in Vietnam and Nepal. A total of 145 samples of filtered groundwater ranging in depth from 3 to 36 m that were analyzed for As (1–1000 μg/L), Fe (0.01–40 mg/L), Mn (0.2–4 mg/L) and S (0.04–14 mg/L) are compared. The P-extractable (0.01–36 mg/kg) and HCl-extractable As (0.04–36 mg/kg) content of the particulate phase was determined in the same suite of samples, in addition to Fe(II)/Fe ratios (0.2–1.0) in the acid-leachable fraction of the particulate phase. Needle-sampler data from Bangladesh indicated a relationship between dissolved As in groundwater and P-extractable As in the particulate phase that was interpreted as an indication of adsorptive equilibrium, under sufficiently reducing conditions, across 3 orders of magnitude in concentrations according to a distribution coefficient of 4 mL/g. The more recent observations from India, Vietnam and Nepal show groundwater As concentrations that are often an order of magnitude lower at a given level of P-extractable As compared to Bangladesh, even if only the subset of particularly reducing intervals characterized by leachable Fe(II)/Fe >0.5 and dissolved Fe >0.2 mg/L are considered. Without attempting to explain why As appears to be particularly mobile in reducing aquifers of Bangladesh compared to the other regions, the consequences of increasing the distribution coefficient for As between the particulate and dissolved phase to 40 mL/g for the flushing of shallow aquifers of their initial As content are explored. 相似文献
13.
Seismic shear‐wave splitting (SWS) monitors the low‐level deformation of fluid‐saturated microcracked rock. We report evidence of systematic SWS changes, recorded above small earthquakes, monitoring the accumulation of stress before earthquakes that allows the time and magnitude of impending large earthquakes to be stress‐forecast. The effects have been seen with hindsight before some 15 earthquakes ranging in magnitude from an M1.7 seismic swarm event in Iceland to the Ms7.7 Chi‐Chi Earthquake in Taiwan, including a successfully stress‐forecast of a M5.0 earthquake in SW Iceland. Characteristic increases in SWS time‐delays are observed before large earthquakes, which abruptly change to deceases shortly before the earthquake occurs. There is a linear relationship between magnitudes and logarithms of durations of both increases and decreases in SWS time‐delays before large impending earthquakes. However, suitably persistent swarms of small earthquakes are too scarce for routine stress‐forecasting. Reliable forecasting requires controlled‐source cross‐hole seismics between neighbouring boreholes in stress‐monitoring sites (SMS). It would be possible to stress‐forecast damaging earthquakes worldwide by a global network of SMS in real time. 相似文献
14.
Richter magnitudes ML have been determined for 718 well recorded South Australian earthquakes by converting amplitudes derived from existing seismograph stations to equivalent Wood‐Anderson amplitudes, and substituting in Richter's formula (Richter 1935), derived for such instruments and for Southern California. The magnitudes so determined were generally found to increase with distance A for each earthquake, at least for events at distances below a few hundred kilometres, reflecting lower attenuation of crustal S waves in South Australia. A distance‐dependent correction, which must be subtracted from Richter magnitudes, was obtained by integrating the weighted least squares fit to the (A, dML/dA) data. The correction increases to one‐half of a magnitude unit at a distance of 400 km, and thereafter decreases smoothly to 0.3 units at 600 km. Station corrections, due to local geological variations, have also been determined. Values range from ‐0.6 to + 0.2 units. Empirical relationships between the revised ML scale and the previously used local magnitude scales mL and MN (White 1968; Stewart 1975) and the body wave magnitude scale mb have been established. The latter yields results consistent with the well known Gutenberg‐Richter formula (Richter 1958) 相似文献
15.
Rakesh Chandra Javid Ahmad Dar Shakil Ahmad Romshoo Irfan Rashid Imtiyaz A. Parvez Sareer Ahmad Mir Midhat Fayaz 《Natural Hazards》2018,93(3):1451-1477
Seismic hazard analysis of the northwest Himalayan belt was carried out by using extreme value theory (EVT). The rate of seismicity (a value) and recurrence intervals with the given earthquake magnitude (b value) was calculated from the observed data using Gutenberg–Richter Law. The statistical evaluation of 12,125 events from 1902 to 2017 shows the increasing trend in their inter-arrival times. The frequency–magnitude relation exhibits a linear downslope trend with negative slope of 0.8277 and positive intercept of 4.6977. The empirical results showed that the annual risk probability of high magnitude earthquake M?≥?7.7 in 50 years is 88% with recurrence period of 47 years, probability of M?≤?7.5 in 50 years is 97% with recurrence period of 27 years, and probability of M?≤?6.5 in 50 years is 100% with recurrence period of 4 years. Kashmir valley, located in the NW Himalaya, encompasses a peculiar tectonic and structural setup. The patterns of the present and historical seismicity records of the valley suggest a long-term strain accumulation along NNW and SSE extensions with the decline in the seismic gap, posing a potential threat of earthquakes in the future. The Kashmir valley is characterized by the typical lithological, tectono-geomorphic, geotechnical, hydrogeological and socioeconomic settings that augment the earthquake vulnerability associated with the seismicity of the region. The cumulative impact of the various influencing parameters therefore exacerbates the seismic hazard risk of the valley to future earthquake events. 相似文献
16.
The b-value of the Gutenberg–Richter’s frequency–magnitude relation and the p-value of the modified Omori law, which describes the decay rate of aftershock activity, were investigated for more than 500 aftershocks in the Aksehir-Afyon graben (AAG) following the 15 December 2000 Sultandagi–Aksehir and the 3 February 2002 Çay–Eber and Çobanlar earthquakes. We used the Kandilli Observatory’s catalog, which contains records of aftershocks with magnitudes ≥2.5. For the Çobanlar earthquake, the estimated b-values for three aftershock sequences are in the range 0.34 ≤ b ≤ 2.85, with the exception of the one that occurred during the first hour (4.77), while the obtained p-values are in the range 0.44 ≤ p ≤ 1.77. The aftershocks of the Sultandagi earthquake have a high p-value, indicating fast decay of the aftershock activity. A regular increase of b can be observed, with b < 1.0 after 0.208 days for the Çay–Eber earthquake. A systematic and similar increase and decrease pattern exists for the b- and p-values of the Çobanlar earthquakes during the first 5 days. 相似文献
17.
E.V. Deev I.D. Zol’nikov I.V. Turova G.G. Rusanov Yu.M. Ryapolova N.N. Nevedrova S.A. Kotler 《Russian Geology and Geophysics》2018,59(4):351-362
Paleoseismological studies confirm that the Uimon basin is thrust by its northern mountain border along the active South Terekta fault. The latest motion along the fault in the 7-8th centuries AD induced an earthquake with a magnitude of Mw= 7.4-7.7 and a shaking intensity of I = 9-11 on the MSK-64 scale. The same fault generated another event (M > 7, I = 9-10), possibly, about 16 kyr ago, which triggered gravity sliding. The rockslide dammed the Uimon valley and produced a lake, where lacustrine deposition began about 14 ± 1 kyr ago, and a later M > 7 (I = 9-10) earthquake at ~ 6 ka caused the dam collapse and the lake drainage. Traces of much older earthquakes that occurred within the Uimon basin are detectable from secondary deformation structures (seismites) in soft sediments deposited during the drainage of a Late Pleistocene ice-dammed lake between 100 and 90 ka and in ~ 77 ka alluvium. The magnitude and intensity of these paleoearthquakes were at least M > 5.0-5.5 and I > 6-7. 相似文献
18.
An attempt has been made to quantify the variability in the seismic activity rate across the whole of India and adjoining
areas (0–45°N and 60–105°E) using earthquake database compiled from various sources. Both historical and instrumental data
were compiled and the complete catalog of Indian earthquakes till 2010 has been prepared. Region-specific earthquake magnitude
scaling relations correlating different magnitude scales were achieved to develop a homogenous earthquake catalog for the
region in unified moment magnitude scale. The dependent events (75.3%) in the raw catalog have been removed and the effect
of aftershocks on the variation of b value has been quantified. The study area was divided into 2,025 grid points (1°×1°) and the spatial variation of the seismicity
across the region have been analyzed considering all the events within 300 km radius from each grid point. A significant decrease
in seismic b value was seen when declustered catalog was used which illustrates that a larger proportion of dependent events in the earthquake
catalog are related to lower magnitude events. A list of 203,448 earthquakes (including aftershocks and foreshocks) occurred
in the region covering the period from 250 B.C. to 2010 A.D. with all available details is uploaded in the website . 相似文献
19.
Sujit Dasgupta Basab Mukhopadhyay Manoj Mukhopadhyay 《Journal of the Geological Society of India》2012,80(3):393-402
The Burmese Arc seismic activity is not uniform for its ∼ 1100 km length; only the Northern Burmese Arc (NBA) is intensely active. Six large earthquakes in the magnitude range 6.1–7.4 have originated from the NBA Benioff zone between 1954–2011, within an area of 200 × 300 km2 where the Indian plate subducts eastward to depths beyond 200 km below the Burma plate. An analysis on seismogenesis of this interplate region suggests that while the subducting lithosphere is characterized by profuse seismicity, seismicity in the overriding plate is rather few. Large earthquakes occurring in the overriding plate are associated with the backarc Shan-Sagaing Fault (SSF) further east. The forecasting performance of the Benioff zone earthquakes in NBA as forerunner is analysed here by: (i) spatial earthquake clustering, (ii) seismic cycles and their temporal quiescence and (iii) the characteristic temporal b-value changes. Three such clusters (C1–C3) are identified from NBA Benioff Zones I & II that are capable of generating earthquakes in the magnitude ranges of 7.38 to 7.93. Seismic cycles evidenced for the Zone I displayed distinct quiescence (Q1, Q2 and Q3) prior to the 6th August 1988 (M 6.6) earthquake. Similar cycles were used to forecast an earthquake (Dasgupta et al. 2010) to come from the Zone I (cluster C1); which, actually struck on 4 February 2011 (M 6.3). The preparatory activity for an event has already been set in the Zone II and we speculate its occurrence as a large event (M > 6.0) possibly within the year 2012, somewhere close to cluster C3. Temporal analysis of b-value indicates a rise before an ensuing large earthquake. 相似文献
20.
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