Centroid moment tensor inversion of low-frequency seismic spectra using Green's functions for aspherical earth models     

Tatsuhiko Hara 《Geophysical Journal International》1997,130(1):251-256

We present a new method for centroid moment tensor (CMT) inversion, in which we employ the Green's function computed for aspherical earth models using the Direct Solution Method. We apply this method to CMT inversion of low-frequency seismic spectra for the 1994 Bolivia and 1996 Flores Sea deep earthquakes. The estimated centroid locations agree well with those obtained by multiple-shock analyses using body-wave data. This shows that it is possible to obtain reliable CMT solutions by analyses of low-frequency seismic spectra using accurate Green's functions computed for present 3-D earth models.  相似文献   

Seismic source study of the Racha-Dzhava (Georgia) earthquake from aftershocks and broad-band teleseismic body-wave records: an example of active nappe tectonics   总被引：1，自引：0，他引：1  

H. Fuenzalida  L. Rivera  H. Haessler  D. Legrand  H. Philip  L. Dorbath    D. McCormack  S. Arefiev  C. Langer  A. Cisternas 《Geophysical Journal International》1997,130(1):29-46

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The Zihuatanejo, Mexico, earthquake of 1994 December 10 (M= 6.6): source characteristics and tectonic implications     

M. Cocco  J. Pacheco  S. K. Singh  F. Courboulex 《Geophysical Journal International》1997,131(1):135-145

An analysis of the Zihuatanejo, Mexico, earthquake of 1994 December 10 ( M = 6.6), based on teleseismic and near-source data, shows that it was a normal-faulting, intermediate-depth ( H = 50 ± 5 km) event. It was located about 30 km inland, within the subducted Cocos plate. The preferred fault plane has an azimuth of 130°, a dip of 79° and a rake of −86°. The rupture consisted of two subevents which were separated in time by about 2 s, with the second subevent occurring downdip of the first. The measured stress drop was relatively high, requiring a Δσ of about a kilobar to explain the high-frequency level of the near-source spectra. A rough estimate of the thickness of the seismogenic part of the oceanic lithosphere below Zihuatanejo, based on the depth and the rupture extent of this event, is 40 km.
This event and the Oaxaca earthquake of 1931 January 15 ( M = 7.8) are the two significant normal-faulting, intermediate-depth shocks whose epicentres are closest to the coast. Both of these earthquakes were preceded by several large to great shallow, low-angle thrust earthquakes, occurring updip. The observations in other subduction zones show just the opposite: normal-faulting events precede, not succeed, updip, thrust shocks. Indeed, the thrust events, soon after their occurrence, are expected to cause compression in the slab, thus inhibiting the occurrence of normal-faulting events. To explain the occurrence of the Zihuatanejo earthquake, we note that the Cocos plate, after an initial shallow-angle subduction, unbends and becomes subhorizontal. In the region of the unbending, the bottom of the slab is in horizontal extension. We speculate that the large updip seismic slip during shallow, low-angle thrust events increases the buckling of the slab, resulting in an incremental tensional stress at the bottom of the slab and causing normal-faulting earthquakes. This explanation may also hold for the 1931 Oaxaca event.  相似文献   

Observability of the isotropic component of a moment tensor     

Hitoshi Kawakatsu 《Geophysical Journal International》1996,126(2):525-544

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Determination of the isotropic component of deep focus earthquakes by inversion of normal-mode data     

Tatsuhiko Hara  Keiko Kuge  Hitoshi Kawakatsu 《Geophysical Journal International》1996,127(2):515-528

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动态指标层析法介绍     

钱晓军  费琪 《地质科技情报》1996,15(3):71-75

参数值是影响模拟结果正确可信的重要因素。介绍了一、二维模拟中参数值确定的动态指标层析法，以及作为其发展基础的由多种热指标确定古充的反演方法，简述了动态指标和热指标相结合的确定参数值层析方法。  相似文献   

中国地下热水分布之特点及属性   总被引：12，自引：0，他引：12  

陈墨香  邓孝 《第四纪研究》1996,16(2):131-138

本文依据我国近年来地下热水资源调研和勘探的新进展及其与有关的研究结果，简述我国地下热水形成和赋存的地热地质背景，分析和归纳构造隆起区中的温泉和中、新生代沉积盆地中的地下热水分布之基本特点，讨论主要水热带的地热学属性和沉积盆地热水的形成机制，为我国地热资源的勘探、开发和今后地球科学有关问题的深化研究提供参考。  相似文献   

塔里木北部地区三叠系储层溶蚀作用机理     

翟晓先  闫华  罗宏  王根长 《新疆地质》1996,(4)

塔里木北部地区三叠系储层在成岩演化过程中曾经历两期溶蚀作用，深埋成岩环境的晚期溶蚀较早期近地表－浅埋成岩环境溶蚀要剧烈得多，溶蚀作用的最大特点是铝硅酸盐矿物较碳酸盐矿物剧烈。溶蚀作用发生的机理是由于三叠系储层处于８０～１２０℃热窗、成岩流体富含低分子量羧酸、碱度由低分子量羧酸控制，铝硅酸盐和碳酸盐矿物均处于去稳定状态。溶蚀作用的发育程度受控于储层砂体的沉积和岩石学特征以及早期成岩发育程度。  相似文献   

成矿流体及成矿机制   总被引：49，自引：0，他引：49  

张文淮  张志坚 《地学前缘》1996,3(4):245-252

根据成矿流体样品——流体包裹体研究资料，目前已知的成矿流体主要有下列四种类型：（１）硅酸盐熔融体＋Ｍ（金属）；（２）Ｈ２Ｏ＋ＮａＣｌ＋Ｍ；（３）Ｈ２Ｏ＋ＣＯ２＋Ｍ；（４）Ｈ２Ｏ＋有机质＋Ｍ。这里所说的Ｈ２Ｏ，实际上是含有一定溶质的盐水；ＣＯ２则还包含有ＣＨ４、ＣＯ、Ｎ２、Ｈ２、Ｈ２Ｓ等等其它组分。不同的矿种、不同成因的矿床与一定种类的成矿流体有关，也就是说，成矿流体具有一定成矿专属性。通过成矿流体研究，我们认为成矿作用主要有下述几种形成机制：（１）不同种类流体混合成矿机制；（２）单一流体不混溶分离成矿机制；（３）流体＋有机质成矿机制；（４）水—岩交换成矿机制；（５）流体物－化条件改变成矿机制。  相似文献   

我国热带亚热带部分地区花岗岩和片麻岩中黑云母风化研究   总被引：5，自引：0，他引：5  

马在平  姜在兴 《矿物岩石》1996,16(2):17-24

综合应用Ｘ射线衍射、扫描电镜、透射电镜及偏光显微镜等技术手段研究了我国热带、亚热带部分地区花岗岩和片麻岩中黑云母的风化现象。结果表明，化学风化产物主要有黑云母／蛭石不规则间层矿物、水黑云母、蛭石、０．７ｎｍ埃洛石及铁的氢氧化物（氧化物）等。影响黑云母风化及次生产物形成的主要因素包括黑云母的晶体结构和化学成分、气候、风化壳母岩的矿物成分等。  相似文献