The west part of Java sits at the transition from oblique subduction of the Australian plate under the Sunda block of the Eurasian plate along Sumatra to orthogonal convergence along central and eastern Java. This region has experienced several destructive earthquakes, the 17 July 2006 Mw 7.7 earthquake and tsunami off the coast of Pangandaran and the 2 September 2009 Mw 7 earthquake, located off the coast of Tasikmalaya. More recently, on 15 December 2017, an Mw 6.5 earthquake occurred off the coast near Pangandaran, and, on 23 January 2018, an Mw 5.9 earthquake occurred offshore Lebak, between Pelabuhan Ratu and Ujung Kulon. Ground shaking and damage occurred locally and in Jakarta on the northern coast of Java. In this study, we use the double‐difference technique to relocate both mainshocks and 10 months of seismicity (228 events) following the earthquakes. The relocation result improved the mainshock locations and depth distribution of earthquakes. Moment tensor of the December 2017 event located the hypocenter at ∼108 km depth within the subducting slab. The best‐fit relocation places the depth at 61 km, close to the slab interface. Aftershocks occur between 68 and 86 km depth and align along a steeper plane than slab geometry models. The January 2018 event is located at ∼46 km depth. Aftershocks form a near‐vertical, pipe‐like structure from the plate interface to ∼10 km depth. A burst of aftershocks immediately following the mainshock shows a shallowing upward trend at a rate of ∼2 km/hr⁠, suggesting that a fluid pressure wave released from the oceanic crust is causing brittle failure in the overriding plate, followed by upward migration of fluids. Five months later, shallow (⁠<25 km⁠) seismicity collocates with background seismicity, suggesting the January 2018 event activated the Pelabuhan Ratu fault system close to the coast.

中文翻译：

---

分析2017年12月15日的6.5兆瓦和2018年1月23日的5.9兆瓦Java地震

爪哇岛的西部处于从沿苏门答腊沿欧亚板块的Sun他区块下的澳大利亚板块的俯冲俯冲到沿爪哇中部和东部的正交收敛的过渡。该地区经历了几次破坏性地震，包括2006年7月17日的7.7兆瓦地震和海啸，以及潘塔干拉海岸附近的2009年9月2日的7兆瓦地震。最近，2017年12月15日，Pangburan附近的海岸附近发生了6.5 Mw地震，2018年1月23日，在Pelabuhan Ratu和Ujung Kulon之间的Lebak海上发生了5.9 Mw地震。本地和爪哇岛北部海岸的雅加达发生了地面震动和破坏。在这个研究中，在地震之后，我们使用双差技术来重新定位主震和10个月的地震活动（228个事件）。搬迁结果改善了地震的主震位置和深度分布。2017年12月事件的矩张量位于俯冲板内约108 km深度的震中。最合适的搬迁深度为61 km，靠近平板界面。余震发生在68至86 km深度之间，并且沿比平板几何模型更陡的平面排列。2018年1月的事件位于约46公里深度处。余震从板块界面到约10 km深度形成近乎垂直的管状结构。紧接在主震之后的余震爆发显示出以〜2 km / hr的速度逐渐变浅的趋势，这表明从洋壳释放的流体压力波在上覆板中引起脆性破坏，随后流体向上迁移。5个月后，浅层地震（⁠<25km⁠）与背景地震活动并存，表明2018年1月的地震激活了靠近海岸的佩拉布汉·拉图断层系统。