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Imaging the Fault Zone Structure of the Shanchio Fault in Taipei Metropolis Using Dark Fiber Distributed Acoustic Sensing

Description: 

The Taipei Metropolis that accommodates around a quarter of Taiwan's population sits on a sedimentary basin bounded by an active normal Fault, the Shanchiao Fault, to the west. While the Shanchiao Fault is capable of generating M 6+ earthquakes, its geometrical and structural characteristics remain poorly constrained due to the absence of outcrops covered by Quaternary alluvial deposits and the lack of high-resolution seismic data. The presence of soft sediments within sedimentary basins and the complex structure of the fault zone both play key roles in modulating seismic waves, resulting in strong amplification and prolonged durations of ground shaking to Taipei city. Here, we utilize the emerging Distributed Acoustic Sensing (DAS) technology to turn an existing telecommunication cable into an ultra-dense linear array across the Shanchiao Fault to investigate the fault and basin structure at unprecedented resolution. We use the ambient noise cross-correlation and beamforming analysis to measure Rayleigh-wave phase velocity dispersion curves along the cable, which are then inverted to obtain a high-resolution 2-D shear-wave velocity profile across the fault. The results show a clear velocity contrast between the Taipei Basin and the Linkou Tableland, delineating the east-dipping geometry and possible damage zone of the Shanchiao Fault. Further spectral ratio analysis also shows obvious frequency‐dependent site amplifications on the side of the Taipei Basin. Our results demonstrate the capability of using ubiquitously existing telecom cables to map detailed fault zone structure and ground motion amplification, which are crucial for urban hazard reduction.

Session: Fiber-optic Sensing Applications in Seismology [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Chi-Hsuan

Student Presenter: Yes

Invited Presentation: 

Poster Number: 63

Authors