A Virtual Subnetwork Approach to Earthquake Early Warning

Abstract

Progress has been made toward the goal of earthquake early warning in Taiwan. By applying the concept of a virtual subnetwork (VSN) to the Taiwan Central Weather Bureau seismic network, the earthquake rapid-reporting time has been reduced to about 30 sec or less by a new system called VSN. This represents a significant step toward realistic earthquake early-warning capability. The VSN system described here was put into operation from December 2000 to June 2001. A total of 54 earthquakes (100% correct detection) were detected and processed successfully during this period. Comprehensive earthquake reports are issued mostly in less than 30 sec, with an average of about 22 sec after the origin time. The 22-sec reporting time will offer more than 20 sec of early-warning time to cities at distances greater than 145 km from the source, for which the shear-wave strong-shaking arrival time is about 44 sec. This 20 sec is an adequate amount of time to carry out numerous preprogrammed emergency-response measures prior to the arrival of strong shaking.

Single-Station Earthquake Characterization for Early Warning

“…Many early warning systems use a network of seismic instruments to determine earthquake magnitude and location (Anderson et al, 1995;Espinosa-Aranda et al, 1995;Wu et al, 1998;Wu and Teng, 2002;Allen and Kanamori, 2003;A. Lockman and R. M. Allen, unpublished manuscript, 2005), but here we focus on a single seismic station's ability to assess earthquake hazard using the first few seconds of the P wave by calculating three parameters needed for early warning: event magnitude, hypocentral distance, and backazimuth.…”

“…The Seismic Alert System in Mexico City uses the peak ground motion measured near the Guerro Gap subduction zone to estimate magnitude, *Present address: Department of Earth and Planetary Science, University of California, Berkeley,307 McCone Hall,Berkeley,rallen@berkeley.edu. and conveys this information to the population in Mexico City, 300 km away, providing 60 sec or more warning of the impending ground motion (Anderson et al, 1995;Espinosa-Aranda et al, 1995). The Central Weather Bureau of Taiwan operates in a similar fashion, and can give a magnitude estimate about 22 sec after the P wave is detected and issue a warning to populations greater than 75 km from the epicenter (Wu et al, 1998;Wu and Teng, 2002).…”

The Status of Earthquake Early Warning around the World: An Introductory Overview

“…In 2001, the first EEW system in Taiwan started operation and continues to be used today. It uses ~100 accelerometers deployed across the island and a Virtual Sub-Net (VSN) algorithm to detect and locate earthquakes and estimate magnitudes using the P-and S-wave energy (Wu and Teng 2002). On average, the system provides warnings 20 s after the origin time, corresponding to when the S wave is ~70 km from the epicenter.…”

Multi-parameter algorithm for Earthquake Early Warning

“…A number of earthquake-prone countries are engaged in ongoing efforts to develop EEW systems having fast on accurate real-time operating EEW algorithm. Japan (Nakamura 1988;Odaka et al 2003;Kamigachi 2009), Mexico (Espinosa-Aranda et al 1995), Taiwan (Wu et al 1999;Wu & Teng 2002, Romania (Wenzel et al 1999;B€ ose et al 2007) and Turkey (Erdik et al 2003;B€ ose et al 2008;Alcik et al 2009) have developed EEW system, which proves effective in mitigating seismic risk at short time scales ). Other countries like California (Allen & Kanamori 2003;Allen et al 2009;Wurman et al 2007;Cua & Heaton 2007), Switzerland (Cua & Heaton 2007) and Italy (Satriano et al 2011) are in early stage of EEW system implementation.…”