青海拉脊山断裂带新活动特征的初步研究
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摘要
拉脊山断裂带由拉脊山北缘断裂和拉脊山南缘断裂两条向NE凸出的弧形断裂所组成 ,分别长约 2 30km和 2 2 0km。它们是介于NNW向的热水 -日月山右旋走滑断裂带和NWW向的西秦岭北缘左旋走滑断裂带之间的一个大型挤压构造区和构造转换带 ,也是分隔拉脊山南北两侧的西宁 -民和盆地和循化 -化隆盆地的重要边界断裂。沿断裂带的追踪考察 ,发现了其新活动的部分地质地貌证据。其最新活动时代为晚更新世晚期 (仅局部为全新世早期 ) ,性质以挤压逆冲为主稍具左旋特征。该断裂的新活动可能导致了该区 2 0余次 5级左右中等地震的发生。可以说 ,拉脊山地区既是反映构造活动 ,又是反映地震活动的地震构造窗。
The Lajishan Mountain fault zone, an arc fault zone which bulge to the NE direction,is consist of two fault zones:the northern margin fault zone and the southern margin fault zone of the Lajishan Mountain.Their lengths are about 230km and 220km,respectively.They are a large scale compressive tectonic area and tectonic transformation zone which are situated between the NNW oriented Reshui-Riyueshan right-lateral strike-slip fault zone and the NWW oriented northern margin fault zone of the west Qinling mountain which is an left-lateral strike-slip fault zone. They are also important boundary fault zones which seqarate the Xining-Minhe basin and the Xunhua-Hualong basin which situated at south and north sides of the Lajishan Mountain.According to the field investigation,the geomorphological evidences indicate that the Lajishan fault zone is still active in late Pleistocene,only a few segments are active in early Holocene,their features are main compressive thrust,a part of areas have left-lateral strike slip components. The newest activity of the fault zone had caused about 20 moderate earthquakes happened on the both sides of the Lajishan mountain since documented history. The Lajishan area is an earthquake tectonic window to reflect the tectonic activity and earthquake activity.
The Lajishan Mountain fault zone, an arc fault zone which bulge to the NE direction,is consist of two fault zones:the northern margin fault zone and the southern margin fault zone of the Lajishan Mountain.Their lengths are about 230km and 220km,respectively.They are a large scale compressive tectonic area and tectonic transformation zone which are situated between the NNW oriented Reshui-Riyueshan right-lateral strike-slip fault zone and the NWW oriented northern margin fault zone of the west Qinling mountain which is an left-lateral strike-slip fault zone. They are also important boundary fault zones which seqarate the Xining-Minhe basin and the Xunhua-Hualong basin which situated at south and north sides of the Lajishan Mountain.According to the field investigation,the geomorphological evidences indicate that the Lajishan fault zone is still active in late Pleistocene,only a few segments are active in early Holocene,their features are main compressive thrust,a part of areas have left-lateral strike slip components. The newest activity of the fault zone had caused about 20 moderate earthquakes happened on the both sides of the Lajishan mountain since documented history. The Lajishan area is an earthquake tectonic window to reflect the tectonic activity and earthquake activity.
引文
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袁道阳、石玉成、刘百篪,1999,青藏高原东北缘地区晚第四纪水系沉积物年代标尺的初步研究,地震地质,21(1),1～8。
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国家地震局兰州地震研究所,1985,陕甘宁青四省区强震目录,西安:陕西科技出版社。
涂德龙、王赞军、曾包红等,1998,青海省湟水盆地全新世活动断裂分布及其活动特征研究,西北地震学报,20(4),83～90。
滕瑞增、金瑶泉、李西侯等,1994,西秦岭北缘断裂带新活动特征,西北地震学报,16(2),85～90。
王二七、张旗,2000,青海拉脊山:一个多阶段抬升的构造窗,地质科学,35(4),493～500。
袁道阳、石玉成、刘百篪,1999,青藏高原东北缘地区晚第四纪水系沉积物年代标尺的初步研究,地震地质,21(1),1～8。
袁道阳、刘小龙、张培震等,2003,青海热水-日月山断裂带的新活动特征,地震地质,25(1),155～166。
袁道阳、张培震、刘百篪等,2004,青藏高原东北缘晚第四纪活动构造的几何图像与构造转换,地质学报,78(2),270～278
。
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