【摘要】 基于中国数字地震台网记录的日本本州地区2009年发生的一次震源深度为167.2km、震级为mb6.0地震的宽频带波形资料,利用二维射线追踪方法给出P波三重震相的理论时-距曲线,并采用试错法构建出与观测时-距曲线拟合效果最优的低速异常模型,发现在中国东部海域下方410 km间断面上、下均存在局部的P波低速异常:300—410 km深度范围内低速异常为4%—5%,而410—460/470 km深度范围内的低速异常则达到4%一7%.结合前人地震层析成像结果,发现该区域不存在明确外源热流,因而,本文认为该低速异常与俯冲板片脱水引起的部分熔融有关.更多还原

【Abstract】 Broadband waveform data for one m_b6.0 earthquake beneath Honshu,Japan,with focal depth of 167.2 km,recorded by China Digital Seismic Network(CDSN) were retrieved.Through trial-and-error method,the anomalous models beneath the Yellow and East China Seas for the six sub-regions were obtained by matching the theoretical travel-time curves of the P triplications from the modified models for the six sub-regions by using 2-D ray tracing with the observed ones.The local lower velocity anomaly appears around the 410 km discontinuity.Above the discontinuity,the P wave velocity decreases by 4%—5%from 300 km to 410 km and below the discontinuty,the velocity decreases by4%—7%from 410 km to 460/470 km.Because thermal flow was not observed by former seismic tomographic restdts.the local low velocity anomaly should be due to the partial-melting caused by the dehydrated water from subducting slab.更多还原