SUMMARY We develop and present a 3-D seismic velocity model of the source region of the 2018 Lombok, Indonesia earthquakes by using local earthquake tomography. The data consist of 28 728 P- and 20 713 S-wave arrival times from 3259 events which were recorded by 20 local seismic stations. The results show that most of the significant earthquakes occur to the edge of high-velocity regions. We interpret these to represent coherent blocks of the Flores Oceanic Crust underthrusting Lombok. At depths shallower than the nucleation area of the largest earthquake, many triggered aftershocks are located within a low-velocity, high-Vp/Vs region which is probably a highly fractured fault zone with a large amount of fluid. This fault zone is parallel to the dip of the Flores Back Arc Thrust and probably ruptured during this earthquake sequence. A prominent low-velocity, high-Vp/Vs region is colocated with the northwest and southern flank of the Rinjani volcanic complex. This large aseismic region is probably related to a wide area of the crust containing fluids due to ongoing magma intrusion beneath the volcano. To the east of Rinjani Volcano a cooled intrusive complex was imaged. It is characterized by high-velocity and low-Vp/Vs, supported by the presence of a high Bouguer anomaly. We confirm the existence of the Sumbawa Strait Strike-Slip Fault and find it is characterized by an elongated low-velocity, high-Vp/Vs zone.

中文翻译：

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印度尼西亚 2018 年龙目岛地震序列震源区局部地震层析成像

总结 我们使用当地地震层析成像技术开发并展示了 2018 年印度尼西亚龙目岛地震震源区的 3-D 地震速度模型。数据包括来自 20 个当地地震台站记录的 3259 个事件的 28 728 个 P 波和 20 713 个 S 波到达时间。结果表明，大部分重大地震发生在高速区边缘。我们将这些解释为代表弗洛雷斯海洋地壳下推龙目岛的连贯块。在比最大地震的成核区更浅的深度，许多触发的余震位于低速、高 Vp/Vs 区域内，该区域可能是具有大量流体的高度断裂的断层带。这个断层带平行于弗洛雷斯弧背冲断层的倾角，很可能在这次地震序列中破裂。一个突出的低速、高 Vp/Vs 区域与 Rinjani 火山复合体的西北侧和南侧位于同一位置。由于火山下方持续不断的岩浆侵入，这个大的抗震区域可能与含有流体的大面积地壳有关。在林贾尼火山以东，一个冷却的侵入复合体被成像。它的特点是高速和低 Vp/Vs，由高布格异常的存在支持。我们确认了松巴哇海峡走滑断层的存在，并发现它的特点是细长的低速、高 Vp/Vs 带。在林贾尼火山以东，一个冷却的侵入复合体被成像。它的特点是高速和低 Vp/Vs，由高布格异常的存在支持。我们确认了松巴哇海峡走滑断层的存在，并发现它的特点是细长的低速、高 Vp/Vs 带。在林贾尼火山以东，一个冷却的侵入复合体被成像。它的特点是高速和低 Vp/Vs，由高布格异常的存在支持。我们确认了松巴哇海峡走滑断层的存在，并发现它的特点是细长的低速、高 Vp/Vs 带。