由小震震源机制解得到的鄂尔多斯周边构造应力场
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摘要
利用格点尝试法首先分区对鄂尔多斯地块周边的 30 0 0多个小震震源机制解进行了处理。结果显示 ,在震源机制解覆盖的时段内 ,地块周边地区的平均构造应力场有以下特征 :地块周边主要以水平构造作用力为主 ,且其主压应力轴走向以地块西南侧为中心 ,从北至东呈扇形展布。在分区基础上 ,对各区的平均主应力轴分布进行了扫描 ,得到了其随时间的变化过程。其中渭河、六盘山和银川区的构造应力场相对稳定 ,临汾和同心区的构造应力场变化复杂 ,临河、包头、呼和、大同和太原区的构造应力场变化与该区的几次中强地震有密切关系。另外 ,地块周边除个别区外大多数区域在 1992年和 1996年前后 ,主压应力轴走向有趋近于N75°E的现象。
This paper discusses mainly the spatial distribution and change of stress orientation at focal depth around the Ordos fault block. The stress orientation are inverted by using the Grid Test Method from more than 3 000 earthquake focal mechanism solutions calculated from earthquakes with magnitude less than 5 recorded by local seismological stations around the Ordos during the years of 1980 to 1999. The region around the Ordos is divided into ten subregions based on neotectonic, geomorphologic and GPS data. The P and T axes being close to horizontal in all subregions implies that the Ordos and its vicinity are dominated by strike-slip motion. The spatial distribution pattern of the principal compressive stress axes around the Ordos Block appears as a fan convex toward the southwest of the Ordos Block. The mean orientation of the P axis is NE-directed in the west, ENE-directed in the north, and nearly E-W-directed in the south of the Ordos Block. In fact, the orientation of P axis in each subregion may vary with time. In 1992 and 1996, the direction of P axis in each subregions was gradually turned toward N75°E direction. Based on the changes of P axis orientation with time in each subregion, three types of subregions are identified: the first type includes the areas where the orientation of P axis is relatively unchanged, such as the Weihe, Liupanshan and Yingchuan subregions; the second type includes the areas where the change of the orientation of P axis with time is complex, such as the Linfen and Tongxin subregions; the third type includes the areas where the orientation of P axis is sensitive to the earthquakes occurred nearby, such as the Datong and Baotou subregions. In Datong and Baotou subregions, the changes of P axis orientation doesn't simultaneously respond to the occurrence of an earthquake; when the direction of P axis in one subregion turns to NNE direction, then an earthquake will occur in this area. However, during the same period, the orientation of P axis in the other subregions doesn't turn to NNE direction. Another interesting thing is that the inconsistency ratio of the Grid Test Method for Datong subregion decreased before the Datong earthquake in 1989, while the ratio for Baotou subregion decreased before the Baotou earthquake in 1996.
This paper discusses mainly the spatial distribution and change of stress orientation at focal depth around the Ordos fault block. The stress orientation are inverted by using the Grid Test Method from more than 3 000 earthquake focal mechanism solutions calculated from earthquakes with magnitude less than 5 recorded by local seismological stations around the Ordos during the years of 1980 to 1999. The region around the Ordos is divided into ten subregions based on neotectonic, geomorphologic and GPS data. The P and T axes being close to horizontal in all subregions implies that the Ordos and its vicinity are dominated by strike-slip motion. The spatial distribution pattern of the principal compressive stress axes around the Ordos Block appears as a fan convex toward the southwest of the Ordos Block. The mean orientation of the P axis is NE-directed in the west, ENE-directed in the north, and nearly E-W-directed in the south of the Ordos Block. In fact, the orientation of P axis in each subregion may vary with time. In 1992 and 1996, the direction of P axis in each subregions was gradually turned toward N75°E direction. Based on the changes of P axis orientation with time in each subregion, three types of subregions are identified: the first type includes the areas where the orientation of P axis is relatively unchanged, such as the Weihe, Liupanshan and Yingchuan subregions; the second type includes the areas where the change of the orientation of P axis with time is complex, such as the Linfen and Tongxin subregions; the third type includes the areas where the orientation of P axis is sensitive to the earthquakes occurred nearby, such as the Datong and Baotou subregions. In Datong and Baotou subregions, the changes of P axis orientation doesn't simultaneously respond to the occurrence of an earthquake; when the direction of P axis in one subregion turns to NNE direction, then an earthquake will occur in this area. However, during the same period, the orientation of P axis in the other subregions doesn't turn to NNE direction. Another interesting thing is that the inconsistency ratio of the Grid Test Method for Datong subregion decreased before the Datong earthquake in 1989, while the ratio for Baotou subregion decreased before the Baotou earthquake in 1996.
引文
安美健,李方全.1998.山西地堑系现今构造应力场〔J〕.地震学报,20(5):461—465.
ANMei jian,LIFang quan.1998.TherecentstressfieldinShanxiGraben〔J〕.ActaSeismologicaSinica,20(5):461—465(inChinese).
啜永清,王赵丽,孟雁英,等.2000.用初动符号的变化识别前震和震群的研究〔J〕.中国地震,16(3):242—255.
CUOYong qing,WANGZhao li,MENGYan ying,etal.2000.Researchondistinguishingforeshockandearth quakeswarmbasedontheinitialmotionchanges〔J〕.EarthquakeResearchinChina,16(3):242—255(inChi nese).
刁桂苓,于新昌.1980.唐山地震前后京、津、唐、张地区的综合断层面解〔J〕.西北地震学报,2(3):39—47.
DIAOGui ling,YUXin chang.1980.CompositefaultplanesolutionsbeforeandafterTangshanShockinJingJinTangZhangregion〔J〕.NorthwesternSeismologicalJournal,2(3):39—47(inChinese).
范俊喜,马瑾,刁桂苓,等.2001.地块活动与成组地震关系的初步探讨〔J〕.地震学报,23(5):515—522.
FANJun xi,MAJin,DIAOGui ling,etal.2001.Correlationbetweenmovementoftectonicblocksandearth quakesingroups〔J〕.ActaSeismologicaSinica,14(5):547—555.
国家地震局鄂尔多斯周缘活动断裂系课题组.1988.鄂尔多斯周缘活动断裂系〔M〕.北京:地震出版社.
TheResearchGrouponActiveFaultSystemaroundOrdosMassif.1988.ActiveFaultSystemaroundOrdosMassif〔M〕.SeismologicalPress,Beijing(inChinese).
姜家兰.1991.陕西及其邻近地区现代构造应力场〔J〕.西北地震学报,13(4):85—88.
JIANGJia lan.1991.RecenttectonicstressfieldinShaanxiProvinceanditsadjacentarea〔J〕.NorthwesternSeis mologicalJournal,13(4):85—88(inChinese).
李孟銮,赵智军.1986.宁夏地区现代构造应力场及其与地震的关系〔J〕.地震研究,9(3):299—313.
LIMeng luan,ZHAOZhi jun.1986.RecenttectonicstressfieldanditsrelationwithearthquakesinNingxiaregion〔J〕.JournalofSeismologicalResearch,9(3):299—313(inChinese).
梁尚鸿,李幼铭,束沛溢,等.1984.利用区域地震台网P、S振幅比资料测定小震震源参数〔J〕.地球物理学报,27(3):247—257.
LIANGShang hong,LIYou ming,SHUPei yi,etal.1984.OnthedeterminingofsourceparametersofsmallearthquakesbyusingamplituderatiosofPandSfromregionalnetworkobservations〔J〕.ActaGeophysicaSini ca,27(3):247—257(inChinese).
刘巍,赵新平,安卫平.1994.太原盆地的应力场特征〔J〕.山西地震,(1):18—24.
LIUWei,ZHAOXin ping,ANWei ping.1994.CharacteristicsofstressfieldinTaiyuanBasin〔J〕.EarthquakeRe searchinShanxi,(1):18—24(inChinese).
刘巍,孟雁英,王赵丽.1995.大同盆地现今构造活动及地壳应力场特征〔J〕.山西地震,(1):7—13.
LIUWei,MENGYan ying,WANGZhao li.1995.PresenttectogenesisandcharacteristicofcrustalstressfieldinDatongBasin〔J〕.EarthquakeResearchinShanxi,(1):7—13(inChinese).
刘巍,安卫平,赵新平.1996.运城盆地的现今构造活动及现代地壳应力场的基本特征〔J〕.山西地震,(2):9—13.
LIUWei,ANWei ping,ZHAOXin ping.1996.RecenttectonicmovementandrecentcrustalstressfieldinYunchengBasin〔J〕.EarthquakeResearchinShanxi,(2):9—13(inChinese).
马瑾.1999.从断层中心论向块体中心论转变〔J〕.地学前缘,6(4):363—369.
MAJin.1999.Changingviewpointfromfaulttoblock—Adiscussionabouttheroleofactiveblockinseismicity〔J〕.EarthScienceFrontiers,6(4):363—369(inChinese).
汪素云,许忠淮.1985.中国东部大陆的地震构造应力场〔J〕.地震学报,7(1):17—32.
WANGSu yun,XUZhong huai.1985.ThetectonicstressfieldineasternChinamainland〔J〕.ActaSeismologicaSinica,7(1):17—32(inChinese).
谢富仁,舒塞兵,窦素芹,等.2000.海原、六盘山断裂带至银川断陷第四纪构造应力场分析〔J〕.地震地质,22(2):139—146.
XIEFu ren,SUSai bing,DOUSu qin,etal.2000.QuaternarytectonicstressfieldintheregionofHaiyuanLiupan shanFaultzonetoYinchuanfaultdepression〔J〕.SeismologyandGeology,22(2):139—146(inChinese).
许向彤,许忠淮,张东宁.1995.求震源机制P波初动解的格点尝试概率法〔J〕.地震地磁观测与研究,16(4):34—42.
XUXiang tong,XUZhong huai,ZHANGDong ning.1995.Aprobabilisticgridtestmethodofdeterminingearth quakefocalmechanismusingP waveonsetpolaritydata〔J〕.SeismologicalandGeomagneticObservationandResearch,16(4):34—42(inChinese).
许忠淮,汪素云,黄雨蕊,等.1989.由大量的地震资料推断的我国大陆构造应力场〔J〕.地球物理学报,32(6):636—646.
XUZhong huai,WANGSu yun,HUANGYu rui,etal.1989.ThetectonicstressfieldofChinesecontinentdeducedfromagreatnumberofearthquakes〔J〕.ActaGeophysicaSinica,32(6):636—646(inChinese).
许忠淮,阎明,赵仲和.1983.由多个小地震推断的?
ANMei jian,LIFang quan.1998.TherecentstressfieldinShanxiGraben〔J〕.ActaSeismologicaSinica,20(5):461—465(inChinese).
啜永清,王赵丽,孟雁英,等.2000.用初动符号的变化识别前震和震群的研究〔J〕.中国地震,16(3):242—255.
CUOYong qing,WANGZhao li,MENGYan ying,etal.2000.Researchondistinguishingforeshockandearth quakeswarmbasedontheinitialmotionchanges〔J〕.EarthquakeResearchinChina,16(3):242—255(inChi nese).
刁桂苓,于新昌.1980.唐山地震前后京、津、唐、张地区的综合断层面解〔J〕.西北地震学报,2(3):39—47.
DIAOGui ling,YUXin chang.1980.CompositefaultplanesolutionsbeforeandafterTangshanShockinJingJinTangZhangregion〔J〕.NorthwesternSeismologicalJournal,2(3):39—47(inChinese).
范俊喜,马瑾,刁桂苓,等.2001.地块活动与成组地震关系的初步探讨〔J〕.地震学报,23(5):515—522.
FANJun xi,MAJin,DIAOGui ling,etal.2001.Correlationbetweenmovementoftectonicblocksandearth quakesingroups〔J〕.ActaSeismologicaSinica,14(5):547—555.
国家地震局鄂尔多斯周缘活动断裂系课题组.1988.鄂尔多斯周缘活动断裂系〔M〕.北京:地震出版社.
TheResearchGrouponActiveFaultSystemaroundOrdosMassif.1988.ActiveFaultSystemaroundOrdosMassif〔M〕.SeismologicalPress,Beijing(inChinese).
姜家兰.1991.陕西及其邻近地区现代构造应力场〔J〕.西北地震学报,13(4):85—88.
JIANGJia lan.1991.RecenttectonicstressfieldinShaanxiProvinceanditsadjacentarea〔J〕.NorthwesternSeis mologicalJournal,13(4):85—88(inChinese).
李孟銮,赵智军.1986.宁夏地区现代构造应力场及其与地震的关系〔J〕.地震研究,9(3):299—313.
LIMeng luan,ZHAOZhi jun.1986.RecenttectonicstressfieldanditsrelationwithearthquakesinNingxiaregion〔J〕.JournalofSeismologicalResearch,9(3):299—313(inChinese).
梁尚鸿,李幼铭,束沛溢,等.1984.利用区域地震台网P、S振幅比资料测定小震震源参数〔J〕.地球物理学报,27(3):247—257.
LIANGShang hong,LIYou ming,SHUPei yi,etal.1984.OnthedeterminingofsourceparametersofsmallearthquakesbyusingamplituderatiosofPandSfromregionalnetworkobservations〔J〕.ActaGeophysicaSini ca,27(3):247—257(inChinese).
刘巍,赵新平,安卫平.1994.太原盆地的应力场特征〔J〕.山西地震,(1):18—24.
LIUWei,ZHAOXin ping,ANWei ping.1994.CharacteristicsofstressfieldinTaiyuanBasin〔J〕.EarthquakeRe searchinShanxi,(1):18—24(inChinese).
刘巍,孟雁英,王赵丽.1995.大同盆地现今构造活动及地壳应力场特征〔J〕.山西地震,(1):7—13.
LIUWei,MENGYan ying,WANGZhao li.1995.PresenttectogenesisandcharacteristicofcrustalstressfieldinDatongBasin〔J〕.EarthquakeResearchinShanxi,(1):7—13(inChinese).
刘巍,安卫平,赵新平.1996.运城盆地的现今构造活动及现代地壳应力场的基本特征〔J〕.山西地震,(2):9—13.
LIUWei,ANWei ping,ZHAOXin ping.1996.RecenttectonicmovementandrecentcrustalstressfieldinYunchengBasin〔J〕.EarthquakeResearchinShanxi,(2):9—13(inChinese).
马瑾.1999.从断层中心论向块体中心论转变〔J〕.地学前缘,6(4):363—369.
MAJin.1999.Changingviewpointfromfaulttoblock—Adiscussionabouttheroleofactiveblockinseismicity〔J〕.EarthScienceFrontiers,6(4):363—369(inChinese).
汪素云,许忠淮.1985.中国东部大陆的地震构造应力场〔J〕.地震学报,7(1):17—32.
WANGSu yun,XUZhong huai.1985.ThetectonicstressfieldineasternChinamainland〔J〕.ActaSeismologicaSinica,7(1):17—32(inChinese).
谢富仁,舒塞兵,窦素芹,等.2000.海原、六盘山断裂带至银川断陷第四纪构造应力场分析〔J〕.地震地质,22(2):139—146.
XIEFu ren,SUSai bing,DOUSu qin,etal.2000.QuaternarytectonicstressfieldintheregionofHaiyuanLiupan shanFaultzonetoYinchuanfaultdepression〔J〕.SeismologyandGeology,22(2):139—146(inChinese).
许向彤,许忠淮,张东宁.1995.求震源机制P波初动解的格点尝试概率法〔J〕.地震地磁观测与研究,16(4):34—42.
XUXiang tong,XUZhong huai,ZHANGDong ning.1995.Aprobabilisticgridtestmethodofdeterminingearth quakefocalmechanismusingP waveonsetpolaritydata〔J〕.SeismologicalandGeomagneticObservationandResearch,16(4):34—42(inChinese).
许忠淮,汪素云,黄雨蕊,等.1989.由大量的地震资料推断的我国大陆构造应力场〔J〕.地球物理学报,32(6):636—646.
XUZhong huai,WANGSu yun,HUANGYu rui,etal.1989.ThetectonicstressfieldofChinesecontinentdeducedfromagreatnumberofearthquakes〔J〕.ActaGeophysicaSinica,32(6):636—646(inChinese).
许忠淮,阎明,赵仲和.1983.由多个小地震推断的?
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