历史大地震破裂区地震危险性的地震活动性定量分析以南北地震带中北段为例

摘要/Abstract

摘要： 尽管地震空区理论在中长期地震预测中起着重要的作用, 但大地震复发在时间上的丛集或非线性行为使得在中长期地震预测研究中依然需要同时考虑非地震空区的、历史地震破裂区的潜在大地震危险性。为了探索能基于观测资料分析的、鉴别历史地震破裂区(包括历史、史前地震破裂的地震空区)大地震复发危险性的技术方法, 在南北地震带中北段挑选出8个具有不同离逝时间的历史大地震破裂区, 分析这些破裂区现代地震活动性的量化特征, 以初步探索判定潜在大地震危险性紧迫程度的地震活动性方法。结果表明, 反映地震序列衰减状态的p值和反映地震活动率的a值与这些历史破裂区最晚大地震的离逝时间有较好的对应关系, 但也有部分破裂区可能由于复杂的断层结构与运动性质, 对应关系并不明确; 反映构造应力积累状况的b值则难于反映离逝时间演化阶段的信息。 b值的时间扫描结果显示, 大部分历史破裂区的b值随时间演化平稳, 但1879年甘肃武都8级地震破裂区的b值则表现为明显的涨落, 并存在持续20年的降低趋势。对比分析认为, 1933年四川茂县7.5级、 1976年四川松潘—平武两次7.2级地震破裂区目前仍处于序列衰减期, 不具备再次发生7级以上地震的背景; 公元842年迭部7级地震破裂区北缘低b值的玛曲段比迭部段更具危险性; 1879年武都8级地震破裂区的b值持续降低也可能反映该区处于新的一轮孕震期。

关键词: 历史破裂区, 大地震危险性, 地震活动性, 南北地震带中北段

Abstract: Although seismic gap theory plays an important role in mid-long term earthquake prediction, the potential risk of the non-seismic gap, historical rupture area, need to be take into consideration at the same time, during the study of mid-long term earthquake prediction, due to the clustering or non-linear behavior of the large earthquake recurrence time. In order to explore technical methods which can be based on observational data, and can indentify historical earthquake rupture zone (including historical, seismic gap of prehistoric earthquake rupture), we select 8 historical large earthquake ruptures with different elapsed times in the South-North Seismic Belt, analyzing the quantitative characteristics of the modern seismicity of these ruptures, to determine the seismicity method of potential earthquake hazard urgency. The results mainly show that, p value, which reflects the attenuation of the earthquake sequence, and a value, which reflects the seismicity rate, are well related to the elapsed time of the latest earthquake in the rupture, that the corresponding relationships in some rupture areas are not clear may due to the complex fault structure and movement behavior. b value, which represents the state of tectonic stress accumulation, is difficult to reflect the elapsed time information of different evolution stages. b value temporal scanning shows that most of the rupture zone evolution is steady over time, but in the rupture zone of the 1879 Wudu M8 earthquake, the b value is manifested in significant fluctuations, and there is a decreasing trend for 20 years. By comparative analyzing, we conclude that the ruptures of the 1933 Maoxian 7.5, the 1976 twin Songpan-Pingwu 7.2 earthquakes, are still in the sequence decay period. Low b values in the Maqu segment, which locates at the north margin of the 842 Diebu M>7 rupture, is more dangerous than the Diebu segment. Continued reduction of b value in the 1879 Wudu M8 earthquake rupture may also reflect a new round of seismogenic period.

Key words: Historical rupture, Seismicity, b value, Mid-north segment of the South-North Seismic Belt

中图分类号:

P315.7

龙锋, 蒋长胜, 冯建刚, 唐兰兰. 历史大地震破裂区地震危险性的地震活动性定量分析以南北地震带中北段为例[J]. 地震, 2012, 32(3): 98-107.

LONG Feng, JIANG Chang-sheng, FENG Jian-gang, TANG Lan-lan. Quantitative Seismicity Analysis for the Risk of Historical Large Earthquake Rupture Zones: Applied to the Mid- north Segment of the South-North Seismic Belt[J]. EARTHQUAKE, 2012, 32(3): 98-107.

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