从震源破裂过程角度分析中国大陆强震面波震级高于矩震级的原因  

Analysis of the Reasons why Surface Wave Magnitude is Higher than Moment Magnitude in the Mainland of China from the Perspective of Source Rupture Parameters

作　　者：许月怡 张勇[1] XU Yueyi;ZHANG Yong(School of Earth and Space Sciences,Peking University,Beijing 100871)

机构地区：[1]北京大学地球与空间科学学院,北京100871

出　　处：《北京大学学报（自然科学版）》2023年第3期407-414,共8页Acta Scientiarum Naturalium Universitatis Pekinensis

基　　金：国家自然科学基金(42021003,42074058)资助。

摘　　要：基于有限断层模型和数值模拟,研究震源参数对面波震级的影响。结果表明,在矩震级相同的情况下,地震破裂持续的时间越短,面波震级就越高,反之亦然。影响地震持续时间的震源参数包括子断层破裂持续时间、破裂速度和破裂长度。若地震矩不变,子断层破裂持续时间和破裂长度与面波震级负相关,破裂速度与面波震级正相关。中国大陆测定的面波震级多数情况下显著高于矩震级的原因可能有二:一是中国大陆发生的强震多为板内地震,由于应力降偏大,破裂持续时间和断层长度可能偏短;二是相对于美国国家地震信息中心测定的Ms(20),中国地震台网中心测定的面波震级系统性地偏大。The influence of the source parameters on Ms is studied through numerical simulations based on finite-fault models.The results show that the Ms is negatively correlated with earthquake rupture duration when moment magnitude remains unchanged.The source parameters that can impact the rupture duration contain the sub-fault duration,rupture velocity,and rupture length.Among them,the sub-fault duration and rupture length is negatively correlated with Ms,while the rupture velocity is positively correlated with Ms,if the moment magnitude remains unchanged.The fact that the measured Ms of strong earthquakes in the mainland of China are significantly larger than moment magnitudes may be due to two reasons.First,the strong earthquakes in the mainland of China are mostly intraplate earthquakes with relatively higher stress drop values,which may have short rupture duration and rupture length.Secondly,Ms determined by China Earthquake Networks Center(CENC)is systematically larger than Ms(20)determined by National Earthquake Information Center.

关 键 词：面波震级 矩震级 震源参数 

分 类 号：P315.32[天文地球—地震学]