2018年帕卢M_(W)7.6地震震源及苏拉威西地区构造应力场特征

Characteristic of Tectonic Stress Field in Source Region of 2018 M7.6 Palu Earthquake and Sulawesi Area

为分析帕卢地震的发震构造及构造应力场特征,基于1976年1月至2018年4月全球CMT目录的震源机制解,反演了2018年9月28日印度尼西亚帕卢地震震源区及苏拉威西地区构造应力场,得到以下初步认识:赤道0°两侧南、北区域的应力场呈现出整体的一致性和局部的不均匀性,北部是以向北倾伏的低倾伏角挤压和向南倾伏的高倾伏角拉张作用为主;南部是近水平的NNW-EW向挤压及低倾伏角的近N-S向拉张的应力状态.摆堆易逆冲推挤及西里伯斯海阻挡导致北部地区的应力场显示俯冲带的特征,也导致北苏拉和马纳都块体的应力场出现差异性.在班达海自东向西的挤压及西部马卡萨盆地的阻挡作用下,南部地区呈现出近E-W向的挤压状态,并沿着NNE-SSW向呈现出地壳物质的构造逃逸现象.深部地幔物质上涌致使苏拉威西中部的R值偏小,形成活火山.受到桑吉双俯冲带和麦纳哈撒海沟的推挤及火山喷发作用,东部交汇区的应力场呈较大倾伏角的拉张为主及R值复杂突变.西部交汇地区的应力场是走滑为主兼有正断应力机制,该应力场有益于此次地震的触发及超剪切波破裂现象的出现.

In order to analyse the characteristic of seismogenic structure and tectonic stress field about Palu earthquake. Based on the focal mechanism solution from Global CMT catalog between January 1976 and April 2018, the tectonic stress field is inverted about Palu Indonesia earthquake on September 28 th, 2018 and Sulawesi area. The conclusions are obtained as follows: Tectonic stress field are consistency and inhomogeneity in both sides of the boundary 0°. The compressive axis is plunging to north with lower plunge and extensional axis is plunging to south with larger plunge in North area. And South area is compressed in the direction of NNW-EW and extended in the direction of N-S with lower plunge. The tectonic stress field in northern area is a subduction zone, and the stress regime is difference in North Sula Block and Manado Block, because of pushing from Batui Thrust and blocking from Celebes Sea. In the south area, the crustal material is escaped in the direction of NNE-SSW, under compression in the direction of E-W, from Banda Sea and Makasa Basin. Lower R value in central Sulawesi is probably caused by mantle flow upwelling from upper mantle. The tectonic stress field and R value are complicated and heterogeneous in eastern area, which is effected by Sanghie double subduction, Minahassa Trench and active volcano. The tectonic stress field is strike slip regime with a little part of normal in western area, which is beneficial to trigger this earthquake and supershear.