Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen-tral-western China     

杨智娴  于湘伟  郑月军  陈运泰  倪晓晞  Winston CHAN 《地震学报(英文版)》2004,17(1):20-30

IntroductionUnderstandingthemechanismofcontinentalearthquakesisveryimportantforseismichaz-ardpreventionandearthquakeprediction.Themodernseismotectonictheoryandtheideaofearthquakepredictionaredevelopedmainlyfromthestudiesoninterplateearthquakes,whicharedifficulttoexplainthephenomenaofintraplateearthquakes,suchasthecontinentalearthquakesoccurredinChinesemainland.Whiletheinterplateearthquakesoccurredalongtheplatebounda-ries,theintraplateearthquakesdistributediffuselyintheinterioroftheplates.Thus…  相似文献   

天津机场地区冻雨天气分析   总被引：28，自引：3，他引：28  

吕胜辉  王积国邱菊 《气象科技》2004,32(6):456-460

利用气象常规资料，对天津机场地区1979～2002年出现的3次冻雨天气进行对比分析，找出了冻雨发生的天气形势特点和大气垂直结构特征：地面受低压控制，高空处在槽前，有明显的增温现象，槽前西南暖湿气流强盛，存在低空急流；850hPa到地面存在逆温层；700～500hPa之间有冰晶层，冰晶层内的温度为-10～-14℃：850hPa附近为暖层，暖层底部的高度在1．0～2．0km左右，暖层的厚度大约为1．0～2．0km，暖层内的温度大约为0～2℃；从地面到1．0～2．0km的高度存在冷层，冷层内温度大约为0～-2℃。以2002年12月13～14日的冻雨天气为代表个例，利用客观分析产品进行诊断分析，总结出冻雨天气预报的着眼点，为冻雨天气预报提供参考。  相似文献   

黄金带油田非均质储层特征及有利目标预测     

张晓玲 《西北地质》2004,37(4):39-43

为了加深对黄金带复杂断块油田进一步开发，针对该区断层复杂、储层变化大、油水关系复杂等特征，笔者综合运用岩心、分析化验及录井、测井资料，对其沉积特征、储层岩性、物性和非均质性进行详细研究。以JASON软件为平台，对含油砂体进行了追踪和预测，并在有利区提出井位部署，为该区的进一步开发提供了地质依据。  相似文献   

非饱和土中镉离子传输模型参数反演   总被引：6，自引：0，他引：6       下载免费PDF全文

崔凯  李宝元  李兴斯  杨国伟 《水科学进展》2004,15(6):700-705

使用自行设计的的真空实验装置,采用一维实验室土柱实验方法在不同实验条件下进行了15组实验,并基于实验所得的穿透曲线,使用梯度正则化方法反演得到了镉离子在8种葡萄牙土样和1种比利时土样中相应的传输模型参数。同时通过数值模拟实验验证了梯度正则化方法的有效性和可靠性,进而证明所得结果是有效的。  相似文献   

Detection of Methane Hydrate-Bearing Zones from Seismic Data     

Takao Inamori  Masami Hato 《Resource Geology》2004,54(1):99-104

Abstract. The MITI Nankai Trough wells were drilled offshore Japan in the Tokai area in 1999 and 2000. The occurrence of methane hydrate was confirmed by various indicators in the borehole logs and from core data. These findings have a large impact on potential future Japanese energy resources and other related-scientific interests.
We first tried to find the methane hydrate-bearing zones using interval velocities derived from NMO velocity analysis. However, this analysis produced poor resolution. To achieve a more detailed delineation of the gas hydrate- and gas-bearing zones, we executed a seismic impedance inversion calibrated by the logs from two of the MITI Nankai Trough wells. Although these two wells are only about 90 m apart, we were able to produce an impedance section with fine detail by adopting a simple initial model and incorporating physical properties of the methane hydrate-bearing zones. The locations of the methane hydrate-bearing zones are readily apparent in the final section.  相似文献   

Imaging the ramp–décollement geometry of the Chelungpu fault using coseismic GPS displacements from the 1999 Chi-Chi, Taiwan earthquake     

Kaj M. Johnson  Paul Segall 《Tectonophysics》2004,378(1-2):123-139

We use coseismic GPS data from the 1999 Chi-Chi, Taiwan earthquake to estimate the subsurface shape of the Chelungpu fault that ruptured during the earthquake. Studies prior to the earthquake suggest a ramp–décollement geometry for the Chelungpu fault, yet many finite source inversions using GPS and seismic data assume slip occurred on the down-dip extension of the Chelungpu ramp, rather than on a sub-horizontal décollement. We test whether slip occurred on the décollement or the down-dip extension of the ramp using well-established methods of inverting GPS data for geometry and slip on faults represented as elastic dislocations. We find that a significant portion of the coseismic slip did indeed occur on a sub-horizontal décollement located at 8 km depth. The slip on the décollement contributes 21% of the total modeled moment release. We estimate the fault geometry assuming several different models for the distribution of elastic properties in the earth: homogeneous, layered, and layered with lateral material contrast across the fault. It is shown, however, that heterogeneity has little influence on our estimated fault geometry. We also investigate several competing interpretations of deformation within the E/W trending rupture zone at the northern end of the 1999 ground ruptures. We demonstrate that the GPS data require a 22- to 35-km-long lateral ramp at the northern end, contradicting other investigations that propose deformation is concentrated within 10 km of the Chelungpu fault. Lastly, we propose a simple tectonic model for the development of the lateral ramp.  相似文献   

Formation and shortening deformation of a back-arc rift basin revealed by deep seismic profiling, central Japan   总被引：1，自引：0，他引：1  

Hiroshi Sato  Takaya Iwasaki  Shinji Kawasaki  Yasutaka Ikeda  Nobuhisa Matsuta  Tetsuya Takeda  Naoshi Hirata  Taku Kawanaka   《Tectonophysics》2004,388(1-4):47

The northern Fossa Magna (NFM) basin is a Miocene rift system produced in the final stages of the opening of the Sea of Japan. It divides the major structure of Japan into two regions, with north-trending geological structures to the NE of the basin and EW trending structures to the west of the basin. The Itoigawa-Shizuoka Tectonic Line (ISTL) bounds the western part of the northern Fossa Magna and forms an active fault system that displays one of the largest slip rates (4–9 mm/year) in the Japanese islands. Deep seismic reflection and refraction/wide-angle reflection profiling were undertaken in 2002 across the northern part of ISTL in order to delineate structures in the crust, and the deep geometry of the active fault systems. The seismic images are interpreted based on the pattern of reflectors, the surface geology and velocities derived from refraction analysis. The 68-km-long seismic section suggests that the Miocene NFM basin was formed by an east dipping normal fault with a shallow flat segment to 6 km depth and a deeper ramp penetrating to 15 km depth. This low-angle normal fault originated as a comparatively shallow brittle/ductile detachment in a high thermal regime present in the Miocene. The NFM basin was filled by a thick (>6 km) accumulation of sediments. Shortening since the late Neogene is accommodated along NS to NE–SE trending thrust faults that previously accommodated extension and produce fault-related folds on their hanging wall. Based on our balanced geologic cross-section, the total amount of Miocene extension is ca. 42 km and the total amount of late Neogene to Quaternary shortening is ca. 23 km.  相似文献   

Low-frequency 3-D seismic survey of upper crustal magmatic intrusions in the northeastern Pannonian basin of Hungary     

Zoltn Hajnal  Endre Heged&#x;s  G. Randy Keller  Tams Fancsik  Attila Cs. Kovcs  Rbert Csabafi 《Tectonophysics》2004,388(1-4):239

A specially designed 700-km² grid survey, deploying 1000 regularly distributed low-frequency seismic recording systems, successfully investigated one of the most complex geologic environments of the Pannonian basin. The wide-angle signals penetrated through over 1000 m of multi-phase igneous lithology and recognized, for the first time, the underlying enigmatic Permian to Early Triassic basement rocks. Tomographic inversion of the first arrival grid data resulted in determination of an accurate three-dimensional (3-D) velocity field, to a depth of 4 km. The anomalous changes of the spatial velocity data outline the regional extent of the Late Miocene magmatic intrusions, which are covered by over 2000 m of Mid-Miocene to Pleistocene clastics. Complex relationship was found between the surface potential data and the intrusive bodies. This multi-faceted geophysical data analysis established a functional technique for mapping a subsurface with intricate acoustic and structural complexity.  相似文献   

用遗传算法反演地壳的变密度模型   总被引：7，自引：1，他引：7  

柯小平  王勇  许厚泽 《武汉大学学报(信息科学版)》2004,29(11):981-984

用青藏高原布格重力异常资料 ,结合亚东 格尔木地学断面得到的Moho面结构 ,反演了青藏高原中部地壳内密度随深度变化的指数分布函数 ,试验得出地壳表层与地幔的密度差约为 - 0 .92 6 g·cm-3 ,地壳的平均密度值为 2 .75 0 g·cm-3 。  相似文献   

Surface wave waveform inversion for variation in upper mantle structure beneath Iceland     

Zhijun Du  G. R. Foulger 《Geophysical Journal International》2004,157(1):305-314

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