Development and Study of Earthworm Platform for Earthquake Early Warning in Taiwan
Date Issued
2015
Date
2015
Author(s)
Chen, Da-Yi
Abstract
For more than 10 years, the Central Weather Bureau of Taiwan has operated an earthquake early warning (EEW) system and has issued warnings for specific agencies. Since 2012 the Earthworm platform in Taiwan has been used to integrate real-time seismic data streams from different types of seismic stations and to monitor seismicity. Using the Earthworm platform, the Earthworm Based Earthquake Alarm Reporting (eBEAR) system is currently in development for shortening reporting times and improving the accuracy of warnings for EEW purposes. The eBEAR system consists of new Earthworm modules for managing P-wave phase picking, trigger associations, hypocenter locations, magnitude estimations, and alert filtering prior to broadcasting. Here, we outline the methodology and performance of the eBEAR system. To calibrate the eBEAR system, an offline test was implemented using 154 earthquakes with magnitudes ranging from ML 4.0 to 6.5. Comparing between the eBEAR and the CWB catalog the results from the offline test show that the epicenter error is about 4.2 km, the standard deviation of magnitude is about 0.3, and the reporting time is about 14.7 s. Additionally, in a comparison of online performance using the current EEW system, the eBEAR system reduced reporting times and improved the accuracy of offshore earthquake locations and magnitudes. Online performance of the eBEAR system indicated that the average reporting times afforded by the system are approximately 15 and 26 s for inland and offshore earthquakes, respectively. The eBEAR system in average can provide more warning time than the current EEW system (3.2 s and 5.5 s for inland and offshore earthquakes, respectively). The eBEAR system now delivers warnings to elementary and junior high schools in Taiwan. For further improving the capabilities of monitoring earthquakes, an EEW system with dense seismic network is constructed by deploying a total of 543 low-cost sensors in Taiwan and incorporating with the official seismic network of Taiwan’s Central Weather Bureau (CWB). The experiment results show that the integrated system can have stable results of source parameters and issue alarms faster (from 14.7 s to 13.1s) than the current system run by only the CWB seismic network (CWBSN).
Subjects
Earthquake Early Warning
Seismic Network
P-wave method
Type
thesis
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