Browsing by Author "Chen, Hongey"

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A first near real-time seismology-based landquake monitoring system
(2017-03-02)
Chao, Wei-An
;
Wu, Yih-Min
;
Zhao, Li
;
Chen, Hongey
;
Chen, Yue-Gau
Hazards from gravity-driven instabilities on hillslope (termed 'landquake' in this study) are an important problem facing us today. Rapid detection of landquake events is crucial for hazard mitigation and emergency response. Based on the real-time broadband data in Taiwan, we have developed a near real-time landquake monitoring system, which is a fully automatic process based on waveform inversion that yields source information (e. g., location and mechanism) and identifies the landquake source by examining waveform fitness for different types of source mechanisms. This system has been successfully tested offline using seismic records during the passage of the 2009 Typhoon Morakot in Taiwan and has been in online operation during the typhoon season in 2015. In practice, certain levels of station coverage (station gap < 180 degrees), signal-to-noise ratio (SNR >= 5.0), and a threshold of event size (volume > 10(6) m(3) and area > 0.20 km(2)) are required to ensure good performance (fitness > 0.6 for successful source identification) of the system, which can be readily implemented in other places in the world with real-time seismic networks and high landquake activities.
Evaluating critical rainfall conditions for large-scale landslides by detecting event times from seismic records
(2018-11-06)
Kuo, Hsien-Li
;
Lin, Guan-Wei
;
Chen, Chi-Wen
;
Saito, Hitoshi
;
Lin, Ching-Weei
One purpose of landslide research is to establish early warning thresholds for rainfall-induced landslides. Insufficient observations of past events have inhibited the analysis of critical rainfall conditions triggering landslides. This difficulty may be resolved by extracting the timing of landslide occurrences through analysis of seismic signals. In this study, seismic records of the Broadband Array in Taiwan for Seismology were examined to identify ground motion triggered by large landslides that occurred in the years 2005 to 2014. A total of 62 landslide-induced seismic signals were identified. The seismic signals were analyzed to determine the timing of landslide occurrences, and the rainfall conditions at those times - including rainfall intensity (I), duration (D), and effective rainfall (Rt) - were assessed. Three common rainfall threshold models (I -D , I-Rt, and Rt-D) were compared, and the crucial factors of a forecast warning model were found to be duration and effective rainfall. In addition, rainfall information related to the 62 landslides was analyzed to establish a critical height of water model, (I - 1.5) . D = 430.2. The critical height of water model was applied to data from Typhoon Soudelor of 2015, and the model issued a large landslide warning for southern Taiwan.