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1.
基于布设在四川威远地区的流动地震台站2019年11月至2020年5月记录的近震波形数据,利用剪切波分裂分析方法获得了研究区内23个地震台站的剪切波分裂参数。结果显示:威远地区地震台站快波偏振方向多数为北西向,与区域主压应力方向一致;有个别台站可能由于受到局部构造环境的影响,快波偏振方向为北东向。而在地壳速度变化明显的威远背斜附近,有6个台站结果显示为两个快波偏振优势方向,表明该地区快波偏振方向是区域应力场和局部构造环境共同作用的结果,威远地区慢波延迟时间均值为4.43 ms/km,威远背斜南侧区域的慢波延迟时间值普遍大于其北部区域,表明在威远地区南部区域的各向异性强度强于北部区域。 相似文献
2.
本研究利用四川紫坪铺水库数字地震台网2004年8月17日~2008年5月11日的地震观测波形资料,使用剪切波分裂SAM系统分析方法,获得了四川紫坪铺水库库区8个数字地震台站的快剪切波偏振结果.结果表明,紫坪铺库区台站的快剪切波偏振优势方向主要为NE或NW方向;台站的快剪切波偏振优势方向与区域主压应力方向或活动断裂走向一致;快剪切波偏振方向变化可能与汶川大地震前区域应力场的增加和龙门山断裂带微破裂增加有关,慢剪切波时间延迟的变化与四川紫坪铺水库水位升降变化相关. 相似文献
3.
本研究使用内蒙古自治区数字测震台网2010年1月至2017年10月区域小地震的波形记录资料,采用SAM方法,进行了地壳剪切波分裂的分析,得到鄂尔多斯块体北缘与西缘地区地壳介质地震各向异性的初步研究结果.根据15个台站161个有效地震记录的分析,鄂尔多斯块体北缘与西缘地区的快剪切波平均偏振方向为NE44.4°±38.4°,慢剪切波平均时间延迟为1.7±1.6ms·km~(-1).研究区域的快剪切波偏振显示出两个优势方向,一个是NE方向,另一个是近NS方向.区内的逆冲凸起与走滑正倾断层构造对剪切波分裂产生了直接的影响,造成了剪切波分裂参数的复杂分布,反映了剪切波分裂参数受到区域应力和构造共同作用的影响.鄂尔多斯块体北缘的快波偏振特征有NE和近NS两个优势偏振方向,其东区与西区的快剪切波偏振表现出明显不同的特征.东区的第一快剪切波优势偏振方向为NE,第二快剪切波优势偏振方向为近NS;西区的第一快剪切波优势偏振方向为近EW,第二快剪切波优势偏振方向为近NS.鄂尔多斯块体北缘的区域背景主压应力方向可能总体上为近NS方向,但空间分布有差异,东区NE方向的优势偏振与西区近EW方向的优势偏振更可能反映了断裂与构造的影响.鄂尔多斯块体西缘的快剪切波偏振特征显示出非常清楚的NE向的优势偏振方向,近NS向的优势偏振方向则不太明显,反映出该地区复杂构造对各向异性分布的影响.慢波时间延迟呈现出西低东高的特点,时间延迟的高值出现在鄂尔多斯块体北缘的东部,时间延迟的这种西低东高的各向异性强度变化,可能反映了区域构造活动西强东弱的特性. 相似文献
4.
通过对云南遥测地震台网2000年1月1日——2003年12月31日4年资料的分析， 使用剪切波分裂SAM综合分析方法，获得了云南地区10个数字地震台站的快剪切波偏振结果. 结果表明， 云南地区大部分台站的快剪切波偏振优势方向主要为近N——S或NNW方向； 位于活动断裂上的台站的快剪切波偏振优势方向与活动断裂的走向一致；与GPS主压应变方向一致，与区域主压应力方向基本一致；少数台站的快剪切波偏振较为复杂，或与活动断裂的走向及GPS主压应变方向不一致. 这样的台站总是位于几个断裂的交会处，反映了复杂的断裂背景和复杂的应力分布特征. 快剪切波偏振优势方向代表了原地最大主压应力方向，受到区域应力场和断裂分布等多种因素的控制. 相似文献
5.
利用雅砻江流域地震台网2011年8月1日至2014年12月31日期间及四川省地震台网1个地震台站2008年5月1日至2015年8月31日期间记录的地震观测波形资料,采用剪切波分裂分析得到了四川锦屏水库地区中上地壳各向异性参数,即快剪切波偏振方向和慢剪切波时间延迟.结果显示,研究区内台站的快波优势偏振方向存在明显的局部特征,左侧4个台站的快波优势偏振方向与区域主压应力方向比较一致,右侧台站优势偏振方向各异.研究发现,台站MLI的快波偏振方向变化与水库水位的变化具有很好的相关性,在2013年7月,水库水位急剧升高到约1800m后,台站的快波偏振方向也发生了90°变化,这是一种被称为90°翻转(90°-flip)的现象.蓄水导致的应力增加(以及可能的渗水)产生的高孔隙压影响了剪切波分裂特征. 相似文献
6.
利用湖北及周边地区数字地震台网2007年12月1日—2013年12月31日的地震观测波形资料,使用剪切波分裂SAM系统分析方法,获得了该地区18个数字地震台站的快剪切波偏振结果。结果表明,湖北地区少部分地震存在S波分裂现象,18个台站的快剪切波偏振优势方向为NE、近NS方向,并无明显的第一优势偏振方向,说明该区台站应力场可能为区域构造背景应力环境与局部断裂诱导的各向异性综合效应;复杂的局部构造会影响剪切波分裂结果,造成偏振优势方向与主要活动断裂走向不一致或与区域主压应力相差较大的现象。 相似文献
7.
主要利用辽宁区域地震台网8个台站记录到的1999年6月至2004年12月的波形数据,采用剪切波分裂SAM分析方法,对辽宁地区的剪切波分裂特征进行了研究。发现大部分台站的快剪切波优势偏振方向为NEE(近EW)向,与原地主压应力方向一致,也与华北北部的区域构造应力场方向一致。然而,辽宁中部的SJ台站和东部的KD台站的快剪切波优势偏振方向分别为近NS向和NW向,与其他台站的结果有差异,可能是受到复杂的局部构造的控制和影响,这2个台站的结果还需要更多资料的证实。根据GPS、地震和地球物理等其它资料,对该地区断层的区域分布、主压应力以及剪切波分裂参数的空间分布特征进行了讨论 相似文献
8.
根据相关函数分析方法，利用唐山地区强地面运动数字台网的资料，进行了剪切波分裂的分析和研究，讨论了唐山地区的地壳中的裂隙各向异性.在1982——1984年的3年里，流动台网中所属21个台站中的16个台站记录到可供研究的地震事件．通过对131个有效记录的计算和分析，得到了唐山地区剪切波分裂的慢剪切波时间延迟和快剪切波偏振方向Paz，并进而计算了该地区的裂隙密度．分析表明，唐山地区的应力场非常复杂，有很强的局部区域特征．由于复杂的断裂分布，16个台站呈现不同的剪切波分裂特征，值分散，Paz各不相同，并且在不止一个台站上观测到以小时为时间间隔的尺度下，和Paz同样是离散的．通过计算，唐山地区，Paz和的平均结果分别为0.007 1 s/km、100和0.022． 相似文献
9.
本文分析了陕西区域地震台网2006年1月到2015年7月的近震波形资料,采用剪切波分裂系统分析方法(SAM),获得了秦岭造山带及两侧区域17个台站的快波偏振方向和慢剪切波时间延迟.结果显示,剪切波分裂参数具有明显的分区特征.鄂尔多斯内部和渭河盆地的台站表现出NE-SW和NEE-SWW向的快波偏振方向,与华北地块区域主压应力方向一致;鄂尔多斯西南部,处于多个地块过渡区,积累了大量的应变,该区快波偏振方向较为复杂,反映了该区复杂的区域构造;南秦岭以勉略缝合带为界,北部为秦岭微板块,南部为扬子地块北缘.秦岭微板块地区台站快剪切波优势偏振方向为NWW-SEE向,与华南地块应力方向一致;扬子地块北缘地区台站表现出NE-SW向的快波优势偏振方向,可能受到青藏高原向东北扩张的影响.本文得到的快剪切波优势偏振方向与秦岭造山带被商丹缝合带和勉略缝合带分割的构造划分方案一致.研究区内,扬子地块北缘地区慢剪切波时间延迟最大,可能反映该区各向异性强于其他区域.本文的研究结果为进一步了解区域应力场特征和动力学过程提供了重要参考. 相似文献
10.
本研究使用首都圈数字地震台网2002年01月～2003年12月的波形记录资料，采用SAM方法，进行了剪切波分裂的分析，得到首都圈西北部地区地壳介质地震各向异性的初步结果.根据对有3条以上可靠记录的14个台站的统计分析，得到首都圈西北部地区的剪切波分裂的统计平均结果为: 快剪切波平均偏振方向为NE699°±445°，慢剪切波平均时间延迟为444±293（ms/km）.研究认为，NE699°±445°的快剪切波平均偏振方向暗示了该区域的水平主压应力方向，快剪切波偏振方向的第一优势取向揭示了NWW近E W方向的原地水平主压应力的构造意义，凸现了NWW向的张家口—蓬莱断陷带.通过快剪切波偏振方向，本研究进一步证实，位于活动断裂上的台站的快剪切波偏振方向的优势取向与断裂走向一致，认为南口—孙河断裂和夏垫断裂是两个活动断裂，而八宝山断裂可能是个并不太活跃的活动断裂.华北盆地里的快剪切波偏振方向显示出复杂的分布特征，对应了盆地凹陷区里许多断裂互相交汇造成区域主压应力场受到局部调整的复杂图像.研究还认为慢剪切波时间延迟急剧的梯度变化可能与地壳深部的温度变化有关联. 相似文献
11.
This study focuses on the southeast Capital area of North China (38.5–39.85° N, 115.5–118.5° E). Shear-wave splitting parameters
at 20 seismic stations are obtained by a systematic analysis method applied to data recorded by the Capital Area Seismograph
Network (CASN) between the years 2002 and 2005. Although some differences in the results are observed, the average fast-wave
polarization is N88.2° W ± 40.7° and the average normalized slow wave time delay is 3.55 ± 2.93 ms/km. The average polarization
is consistent with the regional maximum horizontal compressive stress and also with the maximum principal strain derived from
global positioning system measurements in North China. In spite of the uneven distribution of faults around the array stations
that likely introduce some amount of scatter in the shear-wave splitting measurements, site-dependent polarizations of fast
shear wave are clearly observed: in the northern half of the study area, the polarizations at CASN stations show E–W direction,
whereas in the southern half the polarizations exhibit a variety of possible azimuths, thus suggesting dissimilar stress field
and tectonic frame in both areas. Comparing the splitting results with those previously obtained in the northwest part of
the region, we find a difference in polarization of about 20° between the southeast and northwest parts of the Capital area;
also, in the southeast Capital area the average time delay is smaller than in the northwest Capital area, thus making clear
that the magnitude of crustal seismic anisotropy is not the same in the two zones. Being the shear-wave splitting polarizations
in the southeast Capital area, which lies on the basin, clearly different from the observed polarizations in the northwest
Capital area, where uplifts and basin converge, it is quite evident that the shear-wave splitting results are consequence
of the tectonics and stress field affecting the two regions. 相似文献
12.
Crack－induced anisotropy in the crust from shear wave splitting observed in Tangshan region，North China 总被引：11，自引：0，他引：11
Ｃｒａｃｋ－ｉｎｄｕｃｅｄａｎｉｓｏｔｒｏｐｙｉｎｔｈｅｃｒｕｓｔｆｒｏｍｓｈｅａｒｗａｖｅｓｐｌｉｔｔｉｎｇｏｂｓｅｒｖｅｄｉｎＴａｎｇｓｈａｎｒｅｇｉｏｎ，ＮｏｒｔｈＣｈｉｎａＹｕａｎＧＡＯ（高原）Ｓｉ－ＨｕａＺＨＥＮＧ；（郑斯华）ａｎｄＹｏｎｇ... 相似文献
13.
Sun Yong Zheng SihuaSeismological Bureau of Liaoning Province Shenyang China Center for Analysis Prediction SSB Beijing China 《中国地震研究》1995,(2)
Shear-wave splitting in Tangshan region is studied by using digital seismic data.Analyzing 3-component digital seismic data in Tangshan strong ground motion array,it is found that almost all earthquakes occurred during 1982 to 1984 have significant shear-wave splitting.The polarization directions of faster shear waves in 7 stations are near EW,which are consistent with the axis of maximum principal compressive stress obtained from earthquake fault mechanisms and geodetic surveys.The crack densities of the 7 stations are roughly estimated,0.019 for TS01,TS02 and TS15,0.015 for TS03,TS07 and TS18 and 0.024 for TS19,by using the average time delay of slow shear-wave at the 7 stations. 相似文献
14.
本文利用天山及其邻区布设的37个宽频带地震台站记录到的远震波形数据，分别采用最小能量法和旋转相关法对SKS和SKKS波震相进行了偏振分析，计算出了台站下方介质的S波分裂参数：快波的偏振方向（φ）和慢波延迟时间（δt）.本文研究结果表明：中天山内部大多数台站的各向异性快波方向呈NEE-SWW向，与天山走向平行，慢波时间延迟为0.4～1.7 s，这是塔里木、哈萨克斯坦的南北双向俯冲及其导致的天山地区岩石圈地幔南北向缩短变形的直接反映.本文研究发现中天山北部部分台站下方地震各向异性快波方向与慢波延时随方位角呈现规律性的变化，可能暗示该区上地幔各向异性不能仅用单层水平各向异性这一简单模式来解释.75°E以西的天山地区台站下方S波快波方向和延时具有强烈的横向变化，可能与研究区下方存在的小规模对流有关.中天山不同地段地震台站下方各向异性明显不同，进一步证实了天山地区构造变形的复杂性. 相似文献
15.
Du Xingxin 《Pure and Applied Geophysics》1990,134(2):175-194
Three-component seismograms at the three USC stations, PVP, GFP and DHB, have been examined. Most earthquakes, with magnitudes ranging from 1.4 to 5.0, within a period from 1985 to 1988, show evidence of shear-wave splitting. The preferred polarization of the first split-shear wave arrivals at PVP is nearly in N-S which is consistent with both regional maximum horizontal compressive stress direction and local subsurface fault strike, showing that shear-wave splitting is caused by liquid-filled cracks or fractures associated with the N-S faulting. The polarizations of first shear wave arrivals at GFP are roughly divided into two almost perpendicular directions, ENE-WSW and NNW-SSE, which are parallel or perpendicular to the strike of the geology or topography near the station. Because GFP is near the foothills of Santa Monica Mountains, the shear-wave arrivals may be disturbed by topographic irregularities and by subsurface dipping interfaces. Two examples at DHB clearly display shear-wave splitting. Their polarizations of shear wave are in the direction of N-S, which agree with the fragmentary surface and fracturing direction there. From some relatively reliable delay times, the crack densities at three stations are given, that is, 0.025 at PVP, 0.020 at GFP and 0.045 at DGB. No systematic change of shear-wave polarization is discovered in this study. 相似文献
16.
Crustal seismic anisotropy in Yunnan, Southwestern China 总被引：5，自引：0，他引：5
Using seismic data recorded by Yunnan Telemetry Seismic Network from January 1, 2000, to May 31, 2005, the polarization directions
of fast shear waves are obtained at 15 seismic stations by SAM technique, which is a systematic analysis method on shear-wave
splitting. The results show that predominant directions of polarizations of fast shear waves at most stations are mainly nearly
in the N–S or NNW directions in Yunnan. The predominant polarization directions of fast shear waves at stations located on
the active faults are consistent with the strike of active faults, directions of regional principal compressive strains from
GPS measurement, and directions of regional principal compressive stress. A few of the stations show that polarization patterns
of fast shear waves are more complicated or inconsistent with the strike of active faults and the directions of principal
GPS compressive strains; these stations are always located at the junction of several faults. We conclude that the predominant
polarization direction of fast shear waves indicates that the direction of the in situ maximum principal compressive stress
is controlled by multiple tectonic aspects, such as the regional stress field and faults. 相似文献
17.
Using the cross correlation function analysis method, this paper discusses shear wave splitting and crack-induced anisotropy in the crust beneath Tangshan, North China, by the digital data from Tangshan strong ground motion temporary arrays. Sixteen of twenty-one stations in the arrays recorded earthquake events available for studying from 1982 to 1984. Having calculated 131 available records, we get slower shear wave time delayτ and faster shear wave polarization azimuthPaz in Tangshan region, and the cracks densityε is got further from them. The analysis shows that the stress field is very complicated in Tangshan region and has strongly regional feature. Because of the complicated distribution of faults, different shear wave splitting characteristics are shown in 16 stations, scatteredτ and differentPaz. And they also were observed that theτ andPaz values were diverse within the time scale of hours in more than one station. In Tangshan region the average results ofτ,Paz andε are 0.0071 s · km?1, northwest-west near to east-west and 0.022 respectively. Meantime, the standard deviations were calculated in this paper. 相似文献
18.
The collision of the Indian and Eurasian plates, to the east of the eastern Himalayan syntaxes, forms the Sanjiang lateral collision zone in the southeast margin of the Tibetan Plateau, where there are intense crustal deformation, active faults, earthquakes, as well as a metallogenic belt. Given the lack of adequate seismic data, shear-wave splitting in this area has not been studied. With seismic data from a temporary seismic linear array, as well as permanent seismic stations, this paper adopts the identification on microseismic event to pick more events and obtains shear-wave splitting parameters from local earthquakes. From the west to the east, the study area can be divided into three subzones. The “fast” polarization (i.e. the polarization of the fast shear wave) varies gradually from NNW to NS to NNE in these three subzones. The time delay of the slow shear wave (i.e. the time difference between the two split shear waves) also increases in the same direction, indicating the presence of seismic anisotropy above 25 km in the crust. Both shear-wave splitting parameters are closely related to stress, faults and tectonics. The scatter and the “dual” (i.e. two) dominant orientations of the fast polarizations at several stations indicate strong distortions caused by nearby faults or deep tectonics. The anisotropic parameters are found to be related to some degree to the metallogenic belt. It is worth to further analyse the link between the anisotropic pattern and the metallogenic area, which suggests that shear-wave splitting could be applied to study metallogeny. This paper demonstrates that the identification on microseismic event is a useful tool in detecting shear-wave splitting details and exploring its tectonic implications. 相似文献