The October 20, 2011 Mw 5.1 Talala earthquake in the stable continental region of India     

B. K. Rastogi  Santosh Kumar  Sandeep K. Aggrawal  Kapil Mohan  Nagabhushan Rao  N. Purnachandra Rao  Girish Ch. Kothyari 《Natural Hazards》2013,65(2):1197-1216

The Talala (Sasangir) area in the Saurashtra region of Gujarat, western India, is experiencing tremors since 2001. The swarm type of earthquake activity in 2001, 2004, and every year from 2007 onward has occurred after the monsoon and lasted 2?C3?months each time. In 2007 some 200 shocks (largest M_w 5.0) and in 2011 about 400 shocks down to M1 are well recorded with 1?C2?km location error. The focal depths are about 2?C10?km and shocks are accompanied by blast-like subterranean sounds. The epicenter (21.09?N 70.45E, focal depth: 5?km from location program, 3?km from MTS) of the October 20, 2011 mainshock occurred about 12-km WNW of Talala town or 8-km SSW of the 2007?M _w 5.0 earthquake epicenter. The epicentral trends deciphered from local earthquake data indicate two ENE trends (Narmada trend) for about 50?km length and a conjugate 15-km-long NNW trend (Aravali trend). The focal mechanisms by moment-tensor analysis of full wave forms of two 2007 events of M_w 4.8 and 5.0 and the 2011 event of M_w 5.1 indicate rupture along either of the two trends. The ENE trends follow a gravity low between the gravity highs of Girnar mounts. Seismic reflections also indicate a fault in the area named Girnar Fault. Most of Saurashtra region including the Talala area is covered by Deccan Trap Basalt forming plateaus and conical ridges. There is no major fault within Saurashtra Peninsula though it is believed to have major faults along the boundaries that are non-seismic. The intensity of the October 20, 2011 Talala earthquake is estimated to be 6.5 in MM scale while isoseismals of 6, 5, and 4 and felt distance give M_w 5.1 based on Johnston??s 1994 empirical regressions. The source parameters of the 2011 Talala earthquake are estimated using data from 14 broadband seismograph stations. Estimated seismic moment, moment magnitude, stress drop, corner frequency, and source radius are found to be 10^16.6 N-m, 5.1, 1.6?MPa, 1.3?Hz, and 2,300?m, respectively. The b and p values are obtained to be low, being 0.67 and 0.71, respectively. PGA of 35?cm/sec² is noted and the decay rate of acceleration has been estimated from strong motion data recorded at 5 stations with epicentral distances ranging from 32 to 200?km.  相似文献   

Triggered/migrated seismicity due to the 2001 M w7.7 Bhuj earthquake, Western India     

B. K. Rastogi  Sandeep Kumar Aggrawal  Nagabhushan Rao  Pallabee Choudhury 《Natural Hazards》2013,65(2):1085-1107

Paper describes triggered seismicity to 200?km distance and for a decade due to the 2001 M _w7.7 Bhuj earthquake. The Kachchh region is seismically one of the most active intraplate regions of the World due to the occurrence of two large earthquakes 1819 (M _w7.8) and 2001 (M _w7.7). Though, it has high hazard but was known to have low seismicity in view of the occurrence of fewer smaller shocks. However, the status seems to have changed after 2001. Besides the strong aftershock activity for over a decade, seismicity has spread to nearby faults in Kachchh peninsula and at several places southward for 200?km distance in Saurashtra peninsula. Beyond the rupture zone of the 2001 Bhuj earthquake, more than 40 mainshocks of M _w?~?3?C5 have occurred at 20 different locations, which is unusual. The increased seismicity is inferred to be caused by stress perturbation due to the 2001 Bhuj earthquake by viscoelastic process. In Saurashtra, over and above the viscoelastic stress increase, the transient stress increase by water table rise in monsoons seems to be affecting the timing of mainshocks and associated sequences of earthquakes.  相似文献   

Crystalline and Osmotic Swelling of an Expansive Clay Inundated with Sodium Chloride Solutions     

Sudhakar M. Rao  T. Thyagaraj  P. Raghuveer Rao 《Geotechnical and Geological Engineering》2013,31(4):1399-1404

Compacted expansive clays swell due to crystalline swelling and osmotic/double layer swelling mechanisms. Crystalline swelling is driven by adsorption of water molecules at clay particle surfaces that occurs at inter-layer separations of 10–22 Å. Diffuse double layer swelling occurs at inter-layer separations >22 Å. The tendency of compacted clay to develop osmotic or double layer swelling reduces with increase in solute concentration in bulk solution. This study examines the consequence of increase in solute concentration in bulk solution on the relative magnitudes of the two swelling modes. The objective is achieved by inundating compacted expansive clay specimens with distilled water and sodium chloride solutions in free-swell oedometer tests and comparing the experimental swell with predictions from Van’t Hoff equation. The results of the study indicate that swell potential of compacted expansive clay specimens wetted with relatively saline (0.4, 1 and 4 M sodium chloride) solutions are satisfied by crystalline swelling alone. Comparatively, compacted clay specimens inundated with less saline solutions (0.005–0.1 M sodium chloride) require both crystalline and osmotic swelling to satiate the swell potential.  相似文献   

电法勘探在探测加油站石油烃污染中的应用     

张辉  杨青  胡饶  赵振  孙从军 《物探与化探》2013,(6):1114-1119

对一个有近40年历史的废弃加油站,分别使用探地雷达方法和高密度电阻率法进行探测,同时布置了4口监测井进行取样分析,以验证两种方法探测石油烃类轻质非水相液体(LNAPLs)污染物的准确性。测量结果明确显示了污染源及其扩散范围。实际应用证实了探地雷达与高密度电阻率法可以作为有效的工具在加油站及类似场地用于环境探测。  相似文献   

Impact of pit-toilet leachate on groundwater chemistry and role of vadose zone in removal of nitrate and E. coli pollutants in Kolar District, Karnataka, India     

Sudhakar M. Rao  M. Sekhar  P. Raghuveer Rao 《Environmental Earth Sciences》2013,68(4):927-938

Assessment of chemistry of groundwater infiltrated by pit-toilet leachate and contaminant removal by vadose zone form the focus of this study. The study area is Mulbagal Town in Karnataka State, India. Groundwater level measurements and estimation of unsaturated permeability indicated that the leachate recharged the groundwater inside the town at the rate of 1 m/day. The average nitrate concentration of groundwater inside the town (148 mg/L) was three times larger than the permissible limit (45 mg/L), while the average nitrate concentration of groundwater outside the town (30 mg/L) was below the permissible limit. The groundwater inside the town exhibited E. coli contamination, while groundwater outside the town was free of pathogen contamination. Infiltration of alkalis (Na⁺, K⁺) and strong acids (Cl^?, SO₄ ^2?) caused the mixed Ca–Mg–Cl type (60 %) and Na–Cl type (28 %) facies to predominate groundwater inside the town, while, Ca–HCO₃ (35 %), mixed Ca–Mg–Cl type (35 %) and mixed Ca–Na–HCO₃ type (28 %) facies predominated groundwater outside/periphery of town. Reductions in E. coli and nitrate concentrations with vadose zone thickness indicated its participation in contaminant removal. A 4-m thickness of unsaturated sand + soft, disintegrated weathered rock deposit facilitates the removal of 1 log of E. coli pathogen. The anoxic conditions prevailing in the deeper layers of the vadose zone (>19 m thickness) favor denitrification resulting in lower nitrate concentrations (28–96 mg/L) in deeper water tables (located at depths of ?29 to ?39 m).  相似文献   

Assessment of trace element contamination in soils around Chinnaeru River Basin, Nalgonda District, India   总被引：1，自引：1，他引：0  

G. Machender  Ratnakar Dhakate  G. Tamma Rao  G. Loukya  M. N. Reddy 《Environmental Earth Sciences》2013,70(3):1021-1037

Concentrations of trace elements such as As, Ba, Co, Cr, Cu, Ni, Pb, Rb, Sr, V, Y, Zn and Zr were studied in soils to understand metal contamination due to agriculture and geogenic activities in Chinnaeru River Basin, Nalgonda District, India. This area is affected by the geogenic fluoride contamination. The contamination of the soils was assessed on the basis of geoaccumulation index, enrichment factor (EF), contamination factor and degree of contamination. Forty-four soil samples were collected from the agricultural field from the study area from top 10–50 cm layer of soil. Soil samples were analyzed for trace elements using X-ray fluorescence spectrometer. Data revealed that soils in the study area are significantly contaminated, showing high level of toxic elements than normal distribution. The ranges of concentration of Ba (370–1,710 mg/kg), Cr (8.7–543 mg/kg), Cu (7.7–96.6 mg/kg), Ni (5.4–168 mg/kg), Rb (29.6–223 mg/kg), Sr (134–438 mg/kg), Zr (141.2–8,232 mg/kg) and Zn (29–478 mg/kg). The concentration of other elements was similar to the levels in the earth’s crust or pointed to metal depletion in the soil (EF < 1). The high EFs for some trace elements obtained in soil samples show that there is a considerable heavy metal pollution, which could be due to excessive use of fertilizers and pesticides used for agricultural or may be due to natural geogenic processes in the area. Comparative study has been made with other soil-polluted heavy metal areas and its mobility in soil and groundwater has been discussed. A contamination site poses significant environmental hazards for terrestrial and aquatic ecosystems. They are important sources of pollution and may result in ecotoxicological effects on terrestrial, groundwater and aquatic ecosystems.  相似文献   

Assessment of groundwater inflows into Kuteshwar Limestone Mines through flow modeling study, Madhya Pradesh, India   总被引：1，自引：0，他引：1  

L. Surinaidu  V. V. S. Gurunadha Rao  G. Ramesh 《Arabian Journal of Geosciences》2013,6(4):1153-1161

The development of limestone mining activities in Katni, Madhya Pradesh becomes necessary to increase the depth of exploration to produce ore. Increase in the exploration depth means that mining pits were subjected to water inrush. A hydrological and a hydrogeological model for the Katni area have been developed using USGS flow code, MODFLOW 2000. Collected GIS-based information was synthesized in a finite difference numerical model. The regional steady flow was calibrated under pre-development conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow into the aquifer system due to interaction with river amounts to 14,783 m³/day. Infiltration from precipitation provides 1,600 m³/day of the groundwater supply, while 1,446 m³/day comes from lateral inflow and the remaining. The inflows into mine pit area amounts to 15,725 m³/day. Although the karstic nature of the limestone aquifer the equivalent porous medium flow model is appropriate to represent hydraulic heads and recharge/discharge relationships on a regional scale. The results of this study can be used to predict the required amounts of pumping and the possible locations to dewater the groundwater in the mining pits.  相似文献   

Compton broadening effect on spectral line formation     

A. Peraiah  M. Srinivasa Rao 《Astrophysics and Space Science》2013,343(1):195-211

We have investigated the effects of Compton broadening due to electron scattering in an expanding stellar atmospheres. The line transfer equation is solved by including the second approximation of Edmonds (Astrophys. J. 119:58, 1954) which is due to Compton broadening and obtained the line profiles in (1) plane parallel (PP) (2) spherical (SS) atmospheres. The effect on spectral line formation is studied for different parameters like (a) optical depths (b) densities (c) frequencies (d) temperatures (e) thickness of the atmosphere and (f) expanding velocities. Various combination of the above parameters are used in computing the line profiles observed at infinity. Line profiles are compared for the above said parameters. It is noticed that the expansion of the gases in the atmosphere produces P-Cygni type profiles and at higher optical depths the line profiles change from emission to absorption with their line centers shifting to blue side in the expanding atmospheres.  相似文献   

我国南海历史性水域线的地质特征   总被引：3，自引：1，他引：2  

夏戡原  夏综万  赵明辉  孙珍 《海洋学报》2014,36(5):77-89

40a的海洋地质、地球物理实测研究表明,九段线不仅是显示我国南海主权的历史性水域线,而且总体上也是南海与东部、南部和西部陆区及岛区的巨型地质边界线。根据实测数据,本文将从地质成因、来源、演化的角度论述此南海历史性水域线的合理性。主要结论包括:历史性水域线的东段在地形上基本与马尼拉海沟一致,海沟西侧为南海中央海盆洋壳区,东侧为菲律宾群岛。根据国际地质研究的资料,菲律宾群岛始新世以前位于较偏南的纬度,后来于中晚中新世(距今16~10Ma)仰冲于南海中央海盆之上,因此菲律宾群岛是一个外来群岛。而黄岩岛在马尼拉海沟以西,是中央海盆洋壳区的一个岛礁,与菲律宾群岛成因不同。南海历史性水域线的南段在地形上基本与南沙海槽一致,伴随南沙地块由北部陆缘向南裂离,古南海洋壳沿此海槽以南俯冲至加里曼丹岛陆壳之下,因此南沙地块与加里曼丹陆块为两个来历不同的地块。南海历史性水域线西段的分布在地形上与越东巨型走滑断裂带基本一致,可能与西沙地块、中沙地块、南沙地块从南海北部陆缘向南滑移有关。南沙地块北缘陡直的正断层结构,突显中央海盆是拉裂形成,其基底和中新生代地层与北部珠江口盆地的地层结构可以对比,说明南沙岛礁原属我国华南大陆南缘,后因南海的形成裂离至现今的位置。  相似文献   

基于航渡式水深数据的海底地形DEM建模方法     

贾俊涛  张哲  孟婵媛  周青  谭冀川  李明辉 《海洋测绘》2014,(3):34-36

针对航渡式水深测量资料海量、条带式分布的数据特点,提出了分块抽稀、区域建模、拼接整合的海底地形DEM建模思路,可有效提高不规则形状水深资料的建模效率,丰富海底地形DEM获取手段。实验证明,该方法具有结构简单、操作便利、内存占用少、计算效率高等特点,能够实现基于航渡式水深数据的海底地形DEM建模。  相似文献