时钟不准情形地震精确定位研究——以2011年1月19日安庆地震序列为例

Accurate earthquake location with instrumental clock error: A case study for the 19 January 2011 Anqing earthquake sequence

通过余震序列的精确定位可以较为准确地刻画主震破裂区的时空变化规律.为了减小仪器时钟误差对地震定位精度的影响,本文基于2011年1月19日安庆地震流动台站的S-P到时差,通过主事件和双差地震定位法得到较为准确的主震位置和余震序列时空分布,并评估了仪器时钟误差;又通过对sPL近震深度震相的分析,得到了余震序列较为可靠的深度分布.结果表明,安庆地震发生在宿松—枞阳断裂带附近,余震序列大体近水平分布在5km深度,呈长1.5km、宽1km、高0.3km的薄板状展布;从时空分布来看,随着时间的推移余震序列似乎有往北东方向扩展的趋势.研究表明,基于S-P到时差的定位方法可以有效消除时钟不准确带来的影响,为中小地震和余震序列活动性的研究提供可靠的定位结果.

Accurate locations of aftershoeks are helpful for understanding rup- ture process of the main shock. In order to suppress the impact of instrumental clock error, the arrival-time differences between S and P by the temporary seis- mic array installed after the 19 January 2011 Anqing earthquake were used to re- construct the travel-time data of P and S and more accurate locations of the main shock and aftershocks were obtained by using master event and double-differ- ence earthquake location algorithm~ an algorithm was proposed to estimate the range of clock error~ more reliable depth distribution of the aftershocks was also obtained via analysing sPL, a depth phase at near epicentral distance. The re- sult shows that the Anqing earthquake occurred near Susong-Zongyang fault zone, and the aftershocks concentrated nearly horizontally in the depth range of about 5 kin, spreading in the shape of a thin slab around 1.5 km long, 1.0 km wide and 0. 3 km thick~ the sequence tended to spread northeastward as time went on. The study suggests that earthquake location based on S-P arrival-time difference method can effectively eliminate the influence of clock error, providing reliable results for moderate, minor earthquakes and aftershocks.