High Resolution 3D Shallow Crustal Structure of the Lembang Fault, West Java, Indonesia, produced with Ambient Noise Tomography

Abstract The Lembang Fault is located about eight km north of Bandung City, the capital city of the West Java province of Indonesia, with about 8.79 million people (dated 2020). Several studies state that the Lembang fault is an active fault with a maximum magnitude of 6.5 to 7. In terms of earthquake disaster mitigation, distinguishing characteristics of seismic velocity structures around active faults is critical. This manuscript presents our new research on ambient seismic noise tomography around the Lembang Fault by deploying 73 local temporary seismometer networks to develop a 3D high-resolution shear wave velocity model. We conducted a design acquisition analysis to obtain optimal results using a ray density analysis approach to image the geometry of the Lembang fault with good illumination and resolution, which is essential for identifying shallow geological features. Our result showed that variations in velocity values, both laterally and vertically, were related to variations in the volcanic rock on the near-surface. The geometry of the Lembang Fault and the existence of a low-velocity zone are well-identified from the seismic velocity structure, which low-velocity zone area has the potential for amplifying earthquake waves during an earthquake.