云南景谷MS6.6地震地震动特征分析

Ground Motion Characteristics of the Jinggu MS6.6 Earthquake in Yunnan

摘要:

2014年8月3日云南省鲁甸发生M_S6.5地震后,10月7日云南省内再次发生景谷M_S6.6地震。对我国数字强震台网捕获的39组主震记录进行处理后,分析幅值参数、Arias强度以及持时参数的衰减特征,发现两次地震触发台站远场记录的地震动参数均显著低于预测方程,鲁甸地震的近场地震动参数略高于景谷地震;而鲁甸地震地震动参数衰减快于景谷地震,这可能与云南东部地区Q值低于西部地区的区域差异性特征相关。分析结果可以为研究该区域6.5级左右地震动衰减特征提供参考。

Abstract:

The Jinggu M_S6.6 earthquake that occurred on October 7, 2014 was another shallow earthquake following the Ludian M_S6.5 earthquake that occurred on August 3, 2014 in Yunnan. During the main shock, 39 recordings were obtained by the National Strong Motion Observation Network System of China. Within an area above intensity Ⅵ, only five stations were triggered by the earthquake. In this study, we calculated the peak ground acceleration(PGA) and peak ground velocity(PGV) from these recordings. The PGA and spectral acceleration of site 053JYP, which captured the maximum PGA(543 gal), were significantly higher than the design specifications of a local area. A field survey around this station confirmed that structures were seriously damaged during the main shock. The site and topography effects may be explained by significant differences between the PGAs of sites 053JYZ and 053JGX. We then compared the attenuation characteristics of the PGA, PGV, spectral acceleration, Arias intensity, and significant duration of the Jinggu and Ludian earthquakes. In a near-field area, all observed values of these earthquakes were significantly higher than predicted values but were lower than those predicted in far-field areas. Except for the significant duration, all strong motion parameters from the Ludian earthquake were slightly higher than those of the Jinggu earthquake. We also found most far-field observed values to be lower than those predicted for these two earthquakes. The difference in Q values in different regions of Yunnan may be the main reason for this phenomenon.