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Age estimates of coastal terraces in the Andaman and Nicobar Islands and their tectonic implications
Kusala Rajendran C.P. Rajendran Anil Earnest G.V. Ravi Prasad K. Dutta D.K. Ray R. Anu 《Tectonophysics》2008,455(1-4):53-60
The great Indian Ocean earthquake of December 26, 2004 caused significant vertical changes in its rupture zone. About 800 km of the rupture is along the Andaman and Nicobar Islands, which forms the outer arc ridge of the subduction zone. Coseismic deformation along the exposed land could be observed as uplift/subsidence. Here we analyze the morphological features along the coast of the Andaman and Nicobar Islands, in an effort to reconstruct the past tectonics, taking cues from the coseismic effects. We obtained radiocarbon dates from coastal terraces of the island belt and used them to compute uplift rates, which vary from 1.33 mm yr− 1 in the Little Andaman to 2.80 mm yr− 1 in South Andaman and 2.45 mm yr− 1 in the North Andaman. Our radiocarbon dates converge on 600 yr and 1000 yr old coastal uplifts, which we attribute to the level changes due to two major previous subduction earthquakes in the region. 相似文献
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C. P. Rajendran Kusala Rajendran Majid Shah-hosseini Abdolmajid Naderi Beni C. M. Nautiyal Ronia Andrews 《Natural Hazards》2013,65(1):219-239
Evaluating the hazard potential of the Makran subduction zone requires understanding the previous records of the large earthquakes and tsunamis. We address this problem by searching for earthquake and tectonic proxies along the Makran Coast and linking those observations with the available constraints on historical seismicity and the tell-tale characteristics of sea floor morphology. The earthquake of Mw 8.1 of 1945 and the consequent tsunami that originated on the eastern part of the Makran are the only historically known hazardous events in this region. The seismic status of the western part of the subduction zone outside the rupture area of the 1945 earthquake remains an enigma. The near-shore shallow stratigraphy of the central part of Makran near Chabahar shows evidence of seismically induced liquefaction that we attribute to the distant effects of the 1945 earthquake. The coastal sites further westward around Jask are remarkable for the absence of liquefaction features, at least at the shallow level. Although a negative evidence, this possibly implies that the western part of Makran Coast region may not have been impacted by near-field large earthquakes in the recent past??a fact also supported by the analysis of historical data. On the other hand, the elevated marine terraces on the western Makran and their uplift rates are indicative of comparable degree of long-term tectonic activity, at least around Chabahar. The offshore data suggest occurrences of recently active submarine slumps on the eastern part of the Makran, reflective of shaking events, owing to the great 1945 earthquake. The ocean floor morphologic features on the western segment, on the contrary, are much subdued and the prograding delta lobes on the shelf edge also remain intact. The coast on the western Makran, in general, shows indications of progradation and uplift. The various lines of evidence thus suggest that although the western segment is potentially seismogenic, large earthquakes have not occurred there in the recent past, at least during the last 600?years. The recurrence period of earthquakes may range up to 1,000?years or more, an assessment based on the age of the youngest dated coastal ridge. The long elapsed time points to the fact that the western segment may have accumulated sufficient slip to produce a major earthquake. 相似文献
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Reassessing the earthquake hazard in Kerala based on the historical and current seismicity 总被引：2，自引：0，他引：2
C.P. Rajendran Biju John K. Sreekumari Kusala Rajendran 《Journal of the Geological Society of India》2009,73(6):785-802
Given the lack of proper constraints in understanding earthquake mechanisms in the cratonic interiors and the general absence
of good quality database, here we reassess the seismic hazard in the province of Kerala, a part of the •stable continental
interior•, based on an improved historical and instrumental database. The temporal pattern of the current seismicity suggests
that >60% of the microtremors in Kerala occurs with a time lag after the peak rainfall, indicating that hydroseismicity may
be a plausible model to explain the low-level seismicity in this region. Further, an increment in overall seismicity rate
in the region in the recent years is explained as due to increased anthropogenic activities, which includes changes in hydrological
pathways as a consequence of rapid landscape changes. Our analyses of the historical database eliminate a few events that
are ascribed to this region; this exercise has also led to identification of a few events, not previously noted. The improved
historical database essentially suggests that the central midland region is more prone to seismic activity compared to other
parts of Kerala. This region appears to have generated larger number of significant earthquakes; the most prominent being
the multiple events (doublets) of 1856 and 1953, whose magnitudes are comparable to that of the 2000/2001 (central Kerala)
events. Occurrences of these historical events and the recent earthquakes, and the local geology indicative of pervasive faulting
as shown by widely distributed pseudotachylite veins suggest that the NNW-SSE trending faults in central midland Kerala may
host discrete potentially active sources that may be capable of generating light to moderate size earthquakes. The frequency
of earthquakes in central Kerala evident from the historical database requires that the seismic codes stipulated for this
region are made mandatory. 相似文献
4.
The great 1934 Himalayan earthquake of moment magnitude (Mw) 8.1 generated a large zone of ground failure and liquefaction in north Bihar, India, in addition to the earthquakes of 1833 (Mw ~7.7) and 1988 (Mw 6.7) that have also impacted this region. Here, we present the results of paleoliquefaction investigations from four sites in the plains of north Bihar and one in eastern Uttar Pradesh. The liquefaction features generated by successive earthquakes were dated at AD 829–971, 886–1090, 907–1181, 1130–1376, 1112–1572, 1492–1672, 1733–1839, and 1814–1854. One of the liquefaction events dated at AD 829–971, 886–1090, and 907–1181 may correlate with the great earthquake of AD ~1100, recognized in an earlier study from the sections across the frontal thrust in central eastern Nepal. Two late medieval liquefaction episodes of AD 1130–1376 and 1492–1672 were also exposed in our sites. The sedimentary sections also revealed sandblows that can be attributed to the 1833 earthquake, a lesser magnitude event compared to the 1934. Liquefactions triggered by the 1934 and 1988 earthquakes were evident within the topmost level in some sections. The available data lead us to conjecture that a series of temporally close spaced earthquakes of both strong and large types, not including the infrequent great earthquakes like the 1934, have affected the Bihar Plains during the last 1500 years with a combined recurrence interval of 124?±?63 years. 相似文献
5.
Chávez-García Francisco J. Natarajan Thulasiraman Cárdenas-Soto Martín Rajendran Kusala 《Natural Hazards》2021,105(2):1623-1642
The unusually intense precipitations of the 2018 monsoon triggered numerous landslides in the Western Ghats region, southwest of India. Although the landslides caused no casualties, significant damage to property and infrastructure was observed. We present, as a case study, the results of active and passive seismic prospecting at two of those landslides with the goal of characterizing them, in a first application of shallow seismic exploration to landslides in the region. Our deployments included both sites perturbed by the landslides and unperturbed slopes adjacent to them with the purpose of identifying possible structural differences between slopes that underwent landsliding from slopes that were not affected. We analyze seismic sections obtained using the multi-channel analysis of surface waves technique and compare the results with seismic noise analyzed using seismic interferometry. We show that different analyses give similar results. The lateral variations observed in the shear-wave velocity distribution below the different profiles are well correlated with dominant frequency determined from seismic noise horizontal-to-vertical spectral ratios. Our measurements were taken after the landslides occurred. In hindsight, our results suggest that soil thickness played a major role in the triggering of landslides.
相似文献6.
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Sensitivity of a seismically active reservoir to low-amplitude fluctuations: Observations from Lake Jocassee,South Carolina 总被引：3，自引：0，他引：3
Kusala Rajendran 《Pure and Applied Geophysics》1995,145(1):87-95
Relation between water level changes and pattern of seismicity is an important consideration in studies of Reservoir Induced Seismicity (RIS). Sensitivity of the Regions around Lake Jocassee to small fluctuations in the lake level is presented in this paper. The seismic source regions in the area around the lake seem to be sensitive to changes in the lake level as small as 1 to 1.5 m. Although such changes may produce stress changes of the order of only 0.1 bar, their influence on the spatial pattern of earthquakes seems to be quite perceptible. Observations of this type may help understand the threshold values of pore pressure/effective stress changes that can activate fault zones under high fluid pressure. 相似文献
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C. P. Rajendran Jaishri Sanwal Kristin D. Morell Mike Sandiford B. S. Kotlia John Hellstrom Kusala Rajendran 《Journal of Seismology》2016,20(2):579-594
The central part of the Himalaya (Kumaun and Garhwal Provinces of India) is noted for its prolonged seismic quiescence, and therefore, developing a longer-term time series of past earthquakes to understand their recurrence pattern in this segment assumes importance. In addition to direct observations of offsets in stratigraphic exposures or other proxies like paleoliquefaction, deformation preserved within stalagmites (speleothems) in karst system can be analyzed to obtain continuous millennial scale time series of earthquakes. The Central Indian Himalaya hosts natural caves between major active thrusts forming potential storehouses for paleoseismological records. Here, we present results from the limestone caves in the Kumaun Himalaya and discuss the implications of growth perturbations identified in the stalagmites as possible earthquake recorders. This article focuses on three stalagmites from the Dharamjali Cave located in the eastern Kumaun Himalaya, although two other caves, one of them located in the foothills, were also examined for their suitability. The growth anomalies in stalagmites include abrupt tilting or rotation of growth axes, growth termination, and breakage followed by regrowth. The U-Th age data from three specimens allow us to constrain the intervals of growth anomalies, and these were dated at 4273?±?410 years BP (2673–1853 BC), 2782?±?79 years BP (851–693 BC), 2498?±?117 years BP (605–371 BC), 1503?±?245 years BP (262–752 AD), 1346?±?101 years BP (563–765 AD), and 687?±?147 years BP (1176–1470 AD). The dates may correspond to the timings of major/great earthquakes in the region and the youngest event (1176–1470 AD) shows chronological correspondence with either one of the great medieval earthquakes (1050–1250 and 1259–1433 AD) evident from trench excavations across the Himalayan Frontal Thrust. 相似文献
9.
C.P. Rajendran Kusala Rajendran S. Srinivasalu Vanessa Andrade P. Aravazhi Jaishri Sanwal 《Geoarchaeology》2011,26(6):867-887
Literature of the ancient Chola Dynasty (A.D. 9th–11th centuries) of South India and recent archaeological excavations allude to a sea flood that crippled the ancient port at Kaveripattinam, a trading hub for Southeast Asia, and probably affected the entire South Indian coast, analogous to the 2004 Indian Ocean tsunami impact. We present sedimentary evidence from an archaeological site to validate the textual references to this early medieval event. A sandy layer showing bed forms representing high‐energy conditions, possibly generated by a seaborne wave, was identified at the Kaveripattinam coast of Tamil Nadu, South India. Its sedimentary characteristics include hummocky cross‐stratification, convolute lamination with heavy minerals, rip‐up clasts, an erosional contact with the underlying mud bed, and a landward thinning geometry. Admixed with 1000‐year‐old Chola period artifacts, it provided an optically stimulated luminescence age of 1091 ± 66 yr and a thermoluminescence age of 993 ± 73 yr for the embedded pottery sherds. The dates of these proxies converge around 1000 yr B.P., correlative of an ancient tsunami reported from elsewhere along the Indian Ocean coasts. © 2011 Wiley Periodicals, Inc. 相似文献
10.
The 2001 Mw 7.6 earthquake sourced in the Kachchh rift of northwest India led to extensive damage in the city of Bhuj, located ~70 km southwest of its epicenter. The building stock of this densely populated city was a mix of modern, single, and multistoried structures as well as traditional and non-engineered abodes, most of which were not designed to withstand severe shaking effects. Although there was extensive liquefaction and ground failure in the meizoseismal area, they were not observed in Bhuj, but the damage was severe here. In this study, we apply horizontal to vertical spectral ratio method to ambient vibrations (HVSR-AV) to obtain fundamental resonance frequency (f0) and H/V peak amplitude (A0) to examine if site response had any significant role in the observed damage. The patterns of H/V curves as well as spatial distributions of f0 (0.6–1.4 Hz) and A0 (1.5–4.4) suggest absence of any strong impedance contrast within the subsurface. Similar results obtained for ambient vibrations and earthquake signals suggest the efficacy of the HVSR-AV method as most useful for regions of low-level seismicity. The weathered sandstone that is generally exposed in the city represents the resonating layer whose thickness is approximately estimated as ~66–155 m, based on 1D assumption. The current set of available data precludes any quantitative modeling, but our preliminary inference is that site effects were not significant during the 2001 earthquake damage observed in Bhuj. 相似文献
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