Capability of Tokai Strainmeter Network to Detect and Locate a Slow Slip: First Results

TL;DR

This study evaluates the Tokai Strainmeter Network's ability to detect and locate slow slips, showing high detection probability for M5-class slips and proposing a method to assess network performance for strategic improvements.

Contribution

The paper introduces a modified probability-based completeness method to evaluate TSN's performance in detecting slow slips and explores its application for network extension planning.

Findings

High detection probability (> 0.9) for M5-class slow slips within TSN region.

Detection probability decreases with longer slip durations, especially for M5.5 or larger.

Method can assess performance of network extensions and strategic planning.

Abstract

The Tokai Strainmeter Network (TSN), a dense network deployed in the Tokai region, which is the easternmost region of the Nankai trough, has been designed to monitor slow slips that reflect changes in the coupling state of the plate boundary. It is important to evaluate the current capability of TSN to detect and locate slow slips. For this purpose, the probability-based magnitude of completeness developed for seismic networks was modified to be applicable to the evaluation of TSN's performance. Using 35 slow slips having moment magnitudes M5.1-5.8 recorded by TSN in 2012-2016, this study shows that the probability that TSN detected and located a M5-class slow slip is high (> 0.9) when considering a region in and around the TSN. The probability has been found to depend on the slip duration, especially for M5.5 or larger, namely the longer the duration, the lower the probability. A possible use of this method to assess the network's performance for cases where virtual stations are added to the existing network was explored. The use of this application when devising a strategic plan of the TSN to extend its coverage westwards is proposed. This extension that allows TSN to cover the entire eastern half of the Nankai trough is important, because the historical records show that the eastern half of this trough tends to rupture first.