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1.
The M w 7.8 2015 Gorkha earthquake and its aftershocks significantly impacted the lives and economy of Nepal. The consequences of landslides included fatalities, property losses, blockades of river flow, and damage to infrastructural systems. Co-seismic landslides triggered by this earthquake were significantly widespread and pose a major geodisaster. There were tens of thousands of landslides triggered by the earthquake, majority of which were distributed in between the epicenter of the main shock and the M w 7.3 aftershock. Although 14,670 landslides triggered by this earthquake were identified, only approximately 23% of them were of moderate to large scale with areas greater than 100 m2. Of the moderate- to large-scale landslides identified, just over 90% were triggered by the main shock and smaller aftershocks prior to the major (M w 7.3) aftershock, while nearly 10% were triggered by the ground shaking induced by the major aftershock. Moreover, the number of landslides triggered by the 2015 Gorkha earthquake, specifically by the main shock, was slightly more than the expected number of landslides for the recorded maximum peak ground acceleration (PGA) in comparison to the co-seismic landslides triggered by 26 earthquakes. Over 90% of those moderate- to large-scale landslides were concentrated within the estimated fault rupture surface. Majority of these moderate- to large-scale landslides were disrupted failures with over 96% of which were classified as earth falls. However, the majority of small-scale landslides were rock or boulder falls. The most number of moderate- to large-scale landslides were triggered in the slate, shale, siltstone, phyllite, and schist of the Lesser Himalayan formation followed by an equally significant number in both schist, gneiss, etc. of the Higher Himalayan formation and the phyllite, metasandstone, schist, etc. of the Lesser Himalayan formation. The sizes (i.e., areas) of the landslides were lognormally distributed, with a mode area of 322.0 m2. Slope inclinations of the moderate- to large-scale landslides followed a normal distribution with a mean slope inclination of 32.6° and standard deviation of 13.5°. There exists a strong correlation between the number of landslides and the peak ground acceleration within the study area, specific for different geological formations.  相似文献   

2.
Strong earthquakes in mountainous areas can trigger a large number of landslides that generate deposits of loose and unconsolidated debris across the landscape. These deposits can be easily remobilised by rainfalls, with their movement frequently evolving into catastrophic debris flows and avalanches. This has been the fate of many of the 200,000 co-seismic deposits generated by the 2008 Mw 7.9 Wenchuan earthquake in Sichuan, China. Here we present one of the first studies on the post-seismic patterns of landsliding through a detailed multi-temporal inventory that covers a large portion of the epicentral area (462.5 km2). We quantify changes of size-frequency distribution, active volumes and type of movement. We analyse the possible factors controlling landslide activity and we discuss the significance of mapping uncertainties. We observe that the total number of active landslides decreased with time significantly (from 9189 in 2008 to 221 in 2015), and that post-seismic remobilisations soon after the earthquake (2008–2011) occurred stochastically with respect to the size of the co-seismic deposits. Subsequently (2013–2015), landslide rates remained higher in larger deposits than in smaller ones, particularly in proximity to the drainage network, with channelised flows becoming comparatively more frequent than hillslope slides. However, most of the co-seismic debris remained along the hillslopes and are largely stabilised, urging to rethink the way we believe that seismic activity affects the erosion patterns in mountain ranges.  相似文献   

3.
On 8th August 2017, a magnitude Ms 7.0 earthquake struck the County of Jiuzhaigou, in Sichuan Province, China. It was the third Ms ≥?7.0 earthquake in the Longmenshan area in the last decade, after the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake. The event did not produce any evident surface rupture but triggered significant mass wasting. Based on a large set of pre- and post-earthquake high-resolution satellite images (SPOT-5, Gaofen-1 and Gaofen-2) as well as on 0.2-m-resolution UAV photographs, a polygon-based interpretation of the coseismic landslides was carried out. In total, 1883 landslides were identified, covering an area of 8.11 km2, with an estimated total volume in the order of 25–30?×?106 m3. The total landslide area was lower than that produced by other earthquakes of similar magnitude with strike-slip motion, possibly because of the limited surface rupture. The spatial distribution of the landslides was correlated statistically to a number of seismic, terrain and geological factors, to evaluate the landslide susceptibility at regional scale and to identify the most typical characteristics of the coseismic failures. The landslides, mainly small-scale rockfalls and rock/debris slides, occurred mostly along two NE-SW-oriented valleys near the epicentre. Comparatively, high landslide density was found at locations where the landform evolves from upper, broad valleys to lower, deep-cut gorges. The spatial distribution of the coseismic landslides did not seem correlated to the location of any known active faults. On the contrary, it revealed that a previously-unknown blind fault segment—which is possibly the north-western extension of the Huya fault—is the plausible seismogenic fault. This finding is consistent with what hypothesised on the basis of field observations and ground displacements.  相似文献   

4.
The 2015 Mw7.8 Gorkha earthquake triggered thousands of landslides of various types scattered over a large area. In the current study, we utilized pre- and post-earthquake high-resolution satellite imagery to compile two landslide inventories before and after earthquake and prepared three landslide susceptibility maps within 404 km2 area using frequency ratio (FR) model. From the study, we could map about 519 landslides including 178 pre-earthquake slides and 341 coseismic slides were identified. This study investigated the relationship between landslide occurrence and landslide causative factors, i.e., slope, aspect, altitude, plan curvature, lithology, land use, distance from streams, distance from road, distance from faults, and peak ground acceleration. The analysis showed that the majority of landslides both pre-earthquake and coseismic occurred at slope >30°, preferably in S, SE, and SW directions and within altitude ranging from 1000 to 1500 m and 1500 to 3500 m. Scatter plots between number of landslides per km?2 (LN) and percentage of landslide area (LA) and causative factors indicate that slope is the most influencing factor followed by lithology and PGA for the landslide formation. Higher landslide susceptibility before earthquake is observed along the road and rivers, whereas landslides after earthquake are triggered at steeper slopes and at higher altitudes. Combined susceptibility map indicates the effect of topography, geology, and land cover in the triggering of landslides in the entire basin. The resultant landslide susceptibility maps are verified through AUC showing success rates of 78, 81, and 77%, respectively. These susceptibility maps are helpful for engineers and planners for future development work in the landslide prone area.  相似文献   

5.
We herein present source parameters and focal mechanism of a rare cratonic upper crustal earthquake of Mw4.0, which occurred at 8 km depth (centroid depth) below a region near Deogarh, Jharkhand. For our study, we used broadband waveform data from a seismic network of 15 three-component seismographs in the eastern Indian craton. The average seismic moment, moment magnitude and source radius are estimated to be 1.1 × 1015 N-m, 4.0 and 180.6 m, respectively. The high average stress drop of 14.27 MPa could be attributed to its lower-crustal origin. The mean corner frequency is calculated to be 4.1 Hz. To study the source mechanism, we perform a deviatoric constrained full waveform moment tensor inversion of multiple point sources on the band-passed (0.06 – 0.14 Hz) broadband displacement data of the Deogarh event, using ISOLA software. The best fit is obtained for the source at 8 km centroid depth, with a moment magnitude 3.7, and a right-lateral strike-slip mechanism with strike 162°, dip 72° and rake 169°. The P-axis orients N24°E, which is parallel to the direction of the absolute plate motion direction of Indian plate, while T-axis orients E-W, which is parallel to the strike of the pre-existing Damodar Graben (DG) of Gondwana age. The occurrence of this earthquake is attributed to the neotectonic reactivation of a fault associated with the E-W trending DG shear zone.  相似文献   

6.
Chong Xu  Xiwei Xu  Guihua Yu 《Landslides》2013,10(4):421-431
On 14 April 2010 at 07:49 (Beijing time), a catastrophic earthquake with Ms 7.1 struck Yushu County, Qinghai Province, China. A total of 2,036 landslides were interpreted from aerial photographs and satellite images, verified by selected field checking. These landslides cover about a total area of 1.194 km2. The characteristics and failure mechanisms of these landslides are presented in this paper. The spatial distribution of the landslides is evidently strongly controlled by the locations of the main co-seismic surface fault ruptures. The landslides commonly occurred close together. Most of the landslides are small; there were only 275 individual landslide (13.5 % of the total number) surface areas larger than 1,000 m2. The landslides are of various types. They are mainly shallow, disrupted landslides, but also include rock falls, deep-seated landslides, liquefaction-induced landslides, and compound landslides. Four types of factors are identified as contributing to failure along with the strong ground shaking: natural excavation of the toes of slopes, which mean erosion of the base of the slope, surface water infiltration into slopes, co-seismic fault slipping at landslide sites, and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by the co-seismic ground shaking. To analyze the spatial distribution of the landslides, the landslide area percentage (LAP) and landslide number density (LND) were compared with peak ground acceleration (PGA), distance from co-seismic main surface fault ruptures, elevation, slope gradient, slope aspect, and lithology. The results show landslide occurrence is strongly controlled by proximity to the main surface fault ruptures, with most landslides occurring within 2.5 km of such ruptures. There is no evident correlation between landslide occurrences and PGA. Both LAP and LND have strongly positive correlations with slope gradient, and additionally, sites at elevations between 3,800 and 4,000 m are relatively susceptible to landslide occurrence; as are slopes with northeast, east, and southeast slope aspects. Q4 al-pl, N, and T3 kn 1 have more concentrated landslide activity than others. This paper provides a detailed inventory map of landslides triggered by the 2010 Yushu earthquake for future seismic landslide hazard analysis and also provides a study case of characteristics, failure mechanisms, and spatial distribution of landslides triggered by slipping-fault generated earthquake on a plateau.  相似文献   

7.
Chong Xu  Xiwei Xu 《Natural Hazards》2014,72(2):871-893
The April 14, 2010 Yushu, China, earthquake (Mw 6.9) triggered a great number of landslides. At least 2,036 co-seismic landslides, with a total coverage area of 1.194 km2, were delineated by visual interpretation of aerial photographs and satellite images taken following the earthquake, and verified by field inspection. Based on the mapping results, a statistical analysis of the spatial distribution of these landslides is performed using the landslide area percentage (LAP), defined as the percentage of the area affected by the landslides, and landslide number density (LND), defined as the number of landslides per square kilometer. The purpose is to clarify how the landslides correlate the control factors, which are the elevation, slope angle, slope aspect, slope position, distance from drainages, lithology, distance from the surface rupture, and peak ground acceleration (PGA). The results show that both LAP and LND have strongly positive correlations with slope angle and negative correlations with distance from the surface rupture and distance from drainages. The highest LAP and LPD values are in places of elevations from 3,800 to 4,000 m. The slopes producing landslides are mostly facing toward NE, E, and SE. The geological units of Q4 al-pl, N, and T3 kn 1 have the highest concentrations of co-seismic landslides. No apparent correlations are present between LAP and LND values and PGA. On both sides of the surface rupture, the landslide distributions are almost similar except a few exceptions, likely associated with the nature of the strike-slip seismogenic fault for this event. The bivariate statistical analysis shows that, in descending order, the earthquake-triggered landslide impact factors are distance from surface rupture > slope angle > distance from drainages > lithology > PGA. Besides, as the detailed co-seismic landslides inventories related to strike-slip earthquakes are still few compared with that of thrusting-fault earthquakes, this case study would shed new light on the subject. For instance, the landslide spatial distribution on both sides of the strike-slip seismogenic fault is rather different from that of thrusting-fault earthquakes. It reminds us to take different strategies of measures for prevention and mitigation of landslides induced by earthquakes with different mechanisms.  相似文献   

8.
The devastating Gorkha earthquake (M w 7.8) on April 25, 2015 and its aftershocks triggered numerous landslides across the Lesser and Higher Himalayas of central Nepal. This study aims to characterize these landslides, based on the local topography and geology, and to develop data for landslide hazard zoning. This study focused on a mountainous catchment of the Trishuli River, where a digital elevation model was used to examine hilllslope and river profiles, aerial photos were used to identify 155 coherent landslides, and satellite images were used to map 912 earthquake-induced landslides. The topography of this area is mainly characterized by incised V-shaped inner gorges and steep (> 35°) SW-facing scarp slopes. Although most of the coherent landslides were not reactivated by the earthquakes, the Gogane landslide was affected by the earthquake and partly failed. A majority of the earthquake-induced landslides (91%) were new landslides, while the others were enlarged old landslides. The earthquake-induced landslides occurred mainly on the steep slopes of V-shaped inner gorges and scarp slopes, in gneiss and quartzite strata of the Lesser Himalayas, and they were primarily associated with fractured rock masses. This analysis provides a framework for zoning areas vulnerable to earthquake-induced landslides.  相似文献   

9.
A probabilistic seismic hazard assessment is developed here using maximum credible earthquake magnitude statistics and earthquake perceptibility hazard. Earthquake perceptibility hazard is defined as the probability a site perceives ground shaking equal to or greater than a selected ground motion level X, resulting from an earthquake of magnitude M, and develops estimates for the most perceptible earthquake magnitude, M P(max). Realistic and usable maximum magnitude statistics are obtained from both whole process and part process statistical recurrence models. These approaches are extended to develop relationships between perceptible earthquake magnitude hazard and maximum magnitude recurrence models that are governed by asymptotic and finite return period properties, respectively. Integrated perceptibility curves illustrating the probability of a specific level of perceptible ground motion due to all earthquakes over the magnitude range extending from ?∞ to a magnitude M i are then developed from reviewing site-specific magnitude perceptibility. These lead on to achieving site-specific annual probability of exceedance hazard curves for the example cities of Sofia and Thessaloniki for both horizontal ground acceleration and ground velocity. Both the maximum credible earthquake magnitude M 3 and the most perceptible earthquake magnitude M P(max) are of importance to the earthquake engineer when approaching anti-seismic building design. Both forms of hazard are illustrated using contoured hazard maps for the region bounded by 39°–45°N, 19°–29°E. Patterns are observed for these magnitude hazard estimates—especially M P(max) specific to horizontal ground acceleration and horizontal ground velocity—and compared to inferred patterns of crustal deformation across the region. The full geographic region considered is estimated to be subject to a maximum credible earthquake magnitude M 3—estimated using cumulative seismic moment release statistics—of 7.53 M w, calculated from the full content of the adopted earthquake catalogue, while Bulgaria’s capital, Sofia, is estimated a comparable value of 7.36 M w. Sofia is also forecast most perceptible earthquake magnitudes for the lowest levels considered for horizontal ground acceleration of M PA(50) = 7.20 M w and horizontal ground velocity of M PV(5) = 7.23 M w for a specimen focal depth of 15 km.  相似文献   

10.
In this study, we tracked and analyzed the reconstruction process in Bam, Iran, after the city was struck by an earthquake with a M w of 6.6 on December 26, 2003. We adopted three approaches to comprehensively assess the city’s post-earthquake reconstruction and to shed light on the progress and sustainability of disaster recovery projects. We applied the following methodology. First, we obtained official statistics and reports that included quantitative and qualitative evaluations of the reconstruction process to evaluate the overall outcome of the government’s reconstruction projects. Second, we examined photographs taken during field surveys conducted in 2004, 2007, and 2014 to assess changes within the city. Last, we analyzed three satellite images of Bam—the first taken 3 months before the earthquake, the second immediately after the earthquake, and the third 8 years after the earthquake—to assess the progress of reconstruction work and changes in land cover and land use. The results indicated that considerable progress had been made in reconstructing some of the damaged areas. However, progress was relatively slow in severely damaged areas.  相似文献   

11.

Given the recent historical disastrous tsunamis and the knowledge that the Arabian Gulf (AG) is tectonically active, this study aimed to evaluate tsunami hazards in Kuwait from both submarine earthquakes and subaerial landslides. Despite the low or unknown tsunami risks that impose potential threats to the coastal area’s infrastructures and population of Kuwait, such an investigation is important to sustain the economy and safety of life. This study focused on tsunamis generated by submarine earthquakes with earthquake magnitudes (M w ) of 8.3–9.0 along the Makran Subduction Zone (MSZ) and subaerial landslides with volumes of 0.75–2.0 km3 from six sources along the Iranian coast inside the AG and one source at the Gulf entrance in Oman. The level of tsunami hazards associated with these tsunamigenic sources was evaluated using numerical modeling. Tsunami model was applied to conduct a numerical tsunami simulation and predict tsunami propagation. For landslide sources, a two-layer model was proposed to solve nonlinear longwave equations within two interfacing layers with appropriate kinematic and dynamic boundary conditions. Threat level maps along the coasts of the AG and Kuwait were developed to illustrate the impacts of potential tsunamis triggered by submarine earthquakes of different scales and subaerial landslides at different sources. GEBCO 30 arc-second grid data and others were used as bathymetry and topography data for numerical modeling. Earthquakes of M w 8.3 and M w 8.6 along the MSZ had low and considerable impacts, respectively, at the Gulf entrance, but negligible impacts on Kuwait. An earthquake of M w 9.0 had a remarkable impact for the entire Gulf region and generated a maximum tsunami amplitude of up to 0.5 m along the Kuwaiti coastline 12 h after the earthquake. In the case of landslides inside the AG, the majority impact occurred locally near the sources. The landslide source opposite to Kuwait Bay generated the maximum tsunami amplitudes reaching 0.3 m inside Kuwait Bay and 1.8 m along the southern coasts of Kuwait.

  相似文献   

12.
On May 12, 2008, at 1428 hours (Beijing time), a catastrophic earthquake, with a magnitude of Ms 8.0, struck the Sichuan Province, China. About 200,000 landslides, as a secondary geological hazard associated with the earthquake, were triggered over a broad area. These landslides were of almost all types such as shallow, disrupted landslides, rock falls, deep-seated landslides, and rock avalanches. Some of these landslides damaged and destroyed large part of some towns, blocked roads, dammed rivers, and caused other serious damages. The purpose of this study is to detect correlations between landslide occurrence and the surface rupture plane, ground shaking conditions (measured by peak ground acceleration, PGA), lithology, slope gradient, slope aspect, topographic position, and distance from drainages by using two indices, landslide area percentage (LAP) and the landslide number density (LND), based on geographic information system (GIS) technology and statistical analysis method in a square region (study area) of Beichuan County, Sichuan Province, China. There were 5,096 landslides related with the earthquake which were delineated by visual interpretation and selected field checking throughout the study area. The total area (horizontal projection) of the 5,096 landslides is about 41.103 km2. The LAP, which is defined as the percentage of the plane area affected by landslides, was 10.276 %, and the LND, means the number of landslides per square kilometers, was 12.74 landslides/km2. Statistical analysis results show that both LAP and LND have a positive correlation with slope gradient and a negative correlation with distance from the surface rupture. However, the correlation between the occurrence of landslides with PGA, topographic position, and distance from drainages are uncertain, or has just a little positive correlation. The correlation between landslide and slope aspect also shows the effect of the directivity of the seismic wave. The Zbq formation had the most concentrated landslide activity with the LND value of 21.78 landslides/km , 2 and the ∈1 q Gr. geological units had the highest LAP value. Furthermore, weight index (W i) model is performed with a GIS platform to derive landslide hazard index map. The success rate of the model was 71.615 % and, thus, it was valid. In addition, comparison of five landslide controlling parameters’ influence on landslide occurrences was also carried out.  相似文献   

13.
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   

14.
This paper aims to determine the damage distribution and to analyze the available strong motion records of the April 25, 2015 Nepal earthquake and its eight aftershocks. For this purpose, an earthquake investigation team was dispatched to Nepal from May 6 to 11, 2015 to evaluate the damages of the epicentral region and the four affected cities containing Kathmandu, Bhaktapur, Gorkha, and Pokhara. Based on the observations from the damages to the built environment, an iso-intensity map is prepared on the EMS-98 intensity scale in which the maximum intensity in the epicentral region is estimated to be about VIII. However, based on the geological and geotechnical evidences such as landslide volumes and ground fissures, the maximum intensity can be inferred about IX or X on the International Union for Quaternary Research (INQUA) intensity scale. In addition, the available strong motion data of the 2015 Nepal mainshock and its eight large aftershocks recorded at the KATNP accelerometric station in Kathmandu were processed and analyzed. In order to investigate the probable site effects, the Fourier amplitude spectra (FAS) of the horizontal north-south (N) and east-west (E) components and the average of them (H avg) were divided to the FAS of the vertical (Z) component and thus, the \( \raisebox{1ex}{$ N$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \), \( \raisebox{1ex}{$ E$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \), \( \raisebox{1ex}{${H}_{\mathrm{avg}}$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. \) spectral ratios were calculated. Based on these horizontal to vertical spectral ratios, a low-frequency peak at about 0.2–0.3 Hz (3.5–5-s period) is observed clearly in all the records. Accordingly, the repeated results might imply site amplification due to the thick alluvial deposits and the high groundwater level at the KATNP accelerometric station within the Kathmandu basin. It should be noted that all the horizontal to vertical spectral ratios of the aftershocks show a high peak at around 1.5–3 Hz, which is missed in the horizontal to vertical spectral ratio of the mainshock. On the other hand, considering the low angle of the causative fault plane, a near-source directivity effect on the fault normal direction (here, the vertical component) of the April 25, 2015 mainshock rupture may exist. Therefore, vertical to horizontal spectral ratios (\( \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ N$}\right. \) and \( \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ E$}\right. \)) were also calculated to find the vertical peak more clearly. The figures confirmed a peak at the frequency of 1.5–3 Hz in the mainshock spectra which is not repeated on the aftershock spectra and thus can probably be attributed as the pulse of directivity effect toward Kathmandu. This inferred directivity pulse can be also well distinguished on the velocity and displacement time histories of the mainshock.  相似文献   

15.
The Niumiangou landslide (~7.5 × 106 m3) was the largest that occurred in the town of Yingxiu (the epicentral area) during the 2008 Wenchuan earthquake. This landslide originated on a steep slope (~30°) that was located directly above the rupture surface of the responsible fault and then traveled ~2 km after flowing down the axes of two gently sloping (<12°) valleys. Evidence at the site indicates that the landslide materials were highly fluidized and underwent rapid movement. To examine the initiation and movement mechanisms of this landslide, we performed a detailed field survey, conducted laboratory tests on samples taken from the field, and analyzed the seismic motion. We conclude that the landside materials were displaced due to seismic loading during the earthquake and that liquefaction may have been triggered in saturated layers above the sliding surface with progressive downslope sliding, which resulted in the high mobility of the displaced materials. The liquefaction of colluvial deposits along the travel path due to loading by the sliding mass enhanced the mobility of the displaced mass originating in the source area. Using an energy-based approach, we estimated the dissipated energy in our cyclic loading test and the possible energy dissipated to the soil layer on the slope by the earthquake. We infer that the seismic energy available for the initiation of the slope failure in the source area may have greatly exceeded the amount required for the initiation of the liquefaction failure. The slope instability might have been triggered several seconds after the arrival of seismic motion.  相似文献   

16.
We refine the 1-D velocity model of the Central India Tectonic Zone (CITZ) using well-selected arrival times of P- and S-phases of 354 local earthquakes of magnitude (Mw) between 2.0 and 5.8, recorded by national seismic network from May 1997 to March 2016. Further, we have determined the source mechanisms of 26 selected local events using moment tensor inversion to characterize the dynamics beneath the CITZ. The best-fit simulation between observed and synthetic waveforms obtained the nodal and auxiliary planes of the each faults associated with the earthquake moment magnitude (Mw) for each event. Depth of the fault plane along the CITZ varies from 5 to 38 km. From this study, we found that the western part along the CITZ shows minimum focal depth and reaches maximum 38 kms at Jabalpur in the eastern part. This complex nature of earthquake dynamics occurrence along the CITZ. We propose that the curviplanar the CITZ dominated with sinistral curvature is subjected to compression along the longer ~E–W segments and transtension along shorter segments with ~NE–SW orientations. The occurrences of normal faulting, intrusion of mafic plutons and CLVD mechanisms for earthquakes are interpreted to be linked to the transtension zones and reverse mechanisms associated with the compressions along ~E–W segments.  相似文献   

17.
In this study, the seismicity rate changes that can represent an earthquake precursor were investigated along the Sagaing Fault Zone (SFZ), Central Myanmar, using the Z value technique. After statistical improvement of the existing seismicity data (the instrumental earthquake records) by removal of the foreshocks and aftershocks and man-made seismicity changes and standardization of the reported magnitude scales, 3574 earthquake events with a M w ≥ 4.2 reported during 1977–2015 were found to directly represent the seismotectonic activities of the SFZ. To find the characteristic parameters specifically suitable for the SFZ, seven known events of M w ≥ 6.0 earthquakes were recognized and used for retrospective tests. As a result, utilizing the conditions of 25 fixed earthquake events considered (N) and a 2-year time window (T w), a significantly high Z value was found to precede most of the M w ≥ 6.0 earthquakes. Therefore, to evaluate the prospective areas of upcoming earthquakes, these conditions (N = 25 and T w = 2) were applied with the most up-to-date seismicity data of 2010–2015. The results illustrate that the vicinity of Myitkyina and Naypyidaw (Z = 4.2–5.1) cities might be subject to strong or major earthquakes in the future.  相似文献   

18.
This paper discusses a newly developed high-quality integrated dataset of shallow earthquake ground motions that occurred in Iran, from 1976 to 2013. A total of 860 three-component strong motion records are processed from 183 earthquake events, moment magnitudes 5.0?≤?M w ?≤?7.4, and rupture distances of R RUP  ≤ 120 km. Strong motion data from Iran having special tectonic features and shallow earthquakes with depths less than 35 km are included. This paper presents a thorough procedure used to collect and to generate a database following the Next-Generation Attenuation-West research projects. This database can be used in the development and ranking of ground motion models and for seismological and engineering hazard and risk analyses. Unprocessed strong motion records are obtained from the Iranian Strong Motion Network (ISMN). The time series collected were thoroughly examined through several rounds of quality reviews. The newly generated database includes the peak ground acceleration, peak ground velocity, and pseudo-spectral acceleration for the 5% damped with periods ranging from 0.01 to 10 s. The database also includes ground motion information and source characterization and parameters. This study is the near-source compiled ground motion database that can be used for Iran, and it is consistent with standard worldwide databases.  相似文献   

19.
Some thermal infrared anomalies on the earth’s surface are omens of stronger earthquakes, and have a close relationship with the stress fields. Satellite-based remote sensing is an important means of monitoring and researching this phenomenon. The M S 7.3 Yutian earthquake in Xinjiang on March 20, 2008 and the M S 8.0 Wenchuan earthquake in Sichuan on May 12, 2008 both happened in the Qinghai–Tibet Plateau, China, with epicenters more than 2,000 km apart. The two events, however, were a production of an identical stress field in different developing phases. Prior to the M S 7.3 Yutian earthquake, a large-scale abnormal temperature rise not only covered the epicenter of the forthcoming Yutian earthquake, but also arrived at the epicenter of the farther Wenchuan earthquake. The revolving elliptic stress thermal field reflecting earthquake gestation moved from the west to the east of the Wenchuan epicenter at the time of the Yutian event occurrence. The rotation of the calefactive ellipses and belts prior to the two strong events agreed with the stress field, the focal mechanism, and modality and mechanism property of the ruptures in the crustal surface induced by the events. It should be a reflection of the partial mantle uprush and rotation.  相似文献   

20.
We analyzed macroseismic data and considered the effect of extremely long range propagation of sensible shocks during the deep-focus earthquake in the Sea of Okhotsk on May 24, 2013 (Mw = 8.3). In order to explain this effect, we formulated and qualitatively solved the problem of superposition of P-waves over the radial mode 0S0 of the natural oscillations of the Earth during this earthquake. Our results confirmed the possibility of such an interpretation of the observed macroseismic effect and also allowed us to explain the fact of anomalously low decay of seismic disturbances with distance.  相似文献   

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