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Vertical Arrays Drilled Passing Through an Active Fault With Very Short Recurrence Interval – Investigations and Preliminary Observations

Description: 

Two seismic vertical arrays have been installed at the hanging wall and footwall of the Milun Fault, which caused the 2018 Hualien, Taiwan earthquake with a M_W of 6.4 and ruptured through downtown Hualien city. The Milun Fault is an active fault that has a very short recurrence interval. The previous rupturing occurred in 1951 with an earthquake of magnitude 7.1. To understand the local structure, microtremor array measurements were adopted to investigate S-wave velocities at the two vertical array sites before the drilling. Velocity logging was then used to measure P-wave velocities after drilling. Short-period and strong motion sensors are equipment at the surface and different depths of the two arrays. The measured V_P and V_S profiles are validated to be reliable using the observed ground motion data. The M_W 7.4 earthquake that occurred on April 3^rd, 2024, which was caused by an unknown blind fault, was recorded by the two vertical arrays. The highest intensity was 6-strong during this event according to the intensity scale in Taiwan. Results of the investigations, preliminary observations of ground motions, and site amplification behaviors are studied and introduced.

Session: Station Installations and Site Conditions, a Quest for Improved Strong Motion Database [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Chun-Hsiang

Student Presenter: No

Invited Presentation: 

Poster Number: 61

Authors