地学前缘 ›› 2009, Vol. 16 ›› Issue (1): 218-225.

• 论文 • 上一篇    下一篇

鲜水河—安宁河—则木河断裂带上可能存在的凹凸体:来自背景地震活动性的证据

  

  1. 1上海市地震局, 上海 200062
    2中国地震局 地质研究所, 北京 100029

  • 出版日期:2009-02-02 发布日期:2009-02-02
  • 作者简介:朱艾斓(1966—),女,博士,主要从事小震重新定位、地震活动性与活动构造关系研究。E-mail: alzhu@163.com
  • 基金资助:

    国家科技支撑计划项目(2006BAC13B010101);国家重点基础研究发展计划“973”项目（2004CB418401）；国家自然科学基金项目（40841007）;科学技术部重大基础研究前期研究项目(2003CCB00600)

The possible asperities on the XianshuiheAnningheZemuhe Fault Zone: Evidence from background seismicity

  1. 1Earthquake Administration of Shanghai Municipality, Shanghai 200062, China
    2Institute of Geology, China Earthquake Administration, Beijing 100029, China

  • Online:2009-02-02 Published:2009-02-02

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摘要：

基于1992—2002年小震双差重新定位结果,沿鲜水河—安宁河—则木河断裂带走向的震源剖面作b值及局部复发时间TL值的空间扫描,以确定断裂带上可能存在的凹凸体。结果显示,b值沿断裂带走向具明显的空间非均匀性,与地表几何结构的分段变异是相应的。异常短的TL值及低b值出现在鲜水河断裂带的炉霍—道孚间、安宁河断裂带的石棉—冕宁段以及则木河断裂带的西昌—普格段,表明在间震期这些段落破裂产生的小震平均震级大于其他段落上的小震,是断裂带中相对活跃的段落。由b值与应力成反比的关系,推测这些段落可能为断裂带上凹凸体所在地,成为现今应力积累的闭锁段,是未来主震初始破裂最有可能形成的段落,其中石棉—冕宁段的地震危险性最大。而在鲜水河断裂带南东段的乾宁—康定—石棉一带,尽管历史地震与现今小震都异常活跃,但具有异常高的b值及TL值估计,表明现今应力水平较低,目前可能成为以小震活动为主的蠕滑段,不具大震危险性。

关键词: 凹凸体; 局部复发时间TL值; b值; 鲜水河—安宁河—则木河断裂带; 背景地震活动性

Abstract:

Abstract:  We mapped b value and local recurrence time TL along the 700km long, leftlateral strike slip  XianshuiheAnningheZemuhe fault zone using the relocated microseismicity between 1992 and 2002 that projected onto the cross section to identify the possible locations of asperities Strong variations in b value are observed along the strike of the fault zone, which are consistent with the surface faulting segmentation in geometry The anomalously short local recurrence time TL and low b value estimates appear on the LuhuoDaofu segment of the Xianshuihe fault zone,  the ShimianMianning segment of the Anninghe fault zone, and  the XichangPuge segment of the Zemuhe fault zone, suggesting that these segments may be the relatively active parts that produce relatively larger microearthquakes than average during the inter seismic interval time With the hypothesis that b value is inversely proportional to the stress, we interpret these three segments as the possible asperities on the fault zone, where the future mainshock will be initiated as the high stress has been accumulated there The risk from the ShimianMianning segment is especially noticeable, which is a wellknown historic earthquake gap The anomalously high b value and long TL estimates on the southeastern segment of the Xianshuihe fault zone along QianningKangdingShimian suggest that this segment may be creeping under low stress at present, and no near future mainshock is expected, although both the historic earthquakes and microseismicity are active there

Key words:

Key words: asperity; local recurrence time TL; b value; the XianshuiheAnningheZemuhe fault zone; background seismicity

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