2015年3月新不列颠MS7.4地震震源及邻区构造应力场特征

2015年3月30日至5月15日，巴布亚新几内亚-新不列颠地区发生了一系列地震.为研究该地区的构造应力环境及孕震背景，本文基于Global CMT目录，对新不列颠区域浅部进行构造应力场反演，拟得到高精度的应力图像.反演结果显示：（1）沿着南、北俾斯麦块体边界的区域构造应力场呈走滑体系，最大主压应力轴方位呈SWW-NEE向.（2）所罗门海的NW和NE走向的海沟处于压缩状态，所罗门海块体向新不列颠和所罗门群岛俯冲的板块弯曲部分是局部拉张.（3）受俯冲带的北向推挤，南俾斯麦板块顺时针旋转的挤压，太平洋板块向西部运动汇聚作用，新不列颠岛东北部与新爱尔兰岛南部交汇区域呈现明显非均匀应力状态.（4）此次地震序列的大多数走滑型和逆冲型地震，可能是所罗门海块体俯冲运动，和南俾斯麦块体与太平洋板块的近EW向挤压作用共同引发.

The tectonic stress field in the source of the New Britain MS7.4 earthquake of March 2015 and adjacent areas

A series of earthquakes occurred in New Britain, Papua New Guinea from March 30 to May 15, 2015. This work attempted to determine the stress field in the source region of this event and analyze its preparation mechanism. The focal mechanism solutions in the source and adjacent areas are collected from the global CMT catalogue. The tectonic stress field in the New Britain area is inverted using the focal mechanism data. The results are as follows. (1) The north and south boundary zones of the Bismarck block are in strike-slip stress regime with compressive stress in SWW-NEE diection. (2) The trenches of the Solomon Sea trending NW and NE direction are of compression. The bending portion of the Solomon Sea block subducting beneath the New Britain and Solomon Islands is in an extension state. (3) Under the NS compression of the subduction zone, extrusion caused by the clockwise rotation of the South Bismarck block, and the influence of the westward motion of the Pacific plate, the stress field in the joint region of New Britain and southern New Ireland is extremely heterogeneous. (4) The majority of the strike-slip and thrust earthquakes are produced by both the subducting of the Solomon Sea block and the EW-directed compression between the South Bisimark block and the Pacific plate.