Browsing by Author "Chen, Yue-Gau"

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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.
A First-Layered Crustal Velocity Model for the Western Solomon Islands: Inversion of the Measured Group Velocity of Surface Waves Using Ambient Noise
(2018-11-01)
Ku, Chin-Shang
;
Kuo, Yu-Ting
;
Chao, Wei-An
;
You, Shuei-Huei
;
Huang, Bor-Shouh
Two earthquakes, M-w 8.1 in 2007 and M-w 7.1 in 2010, hit the western province of the Solomon Islands and caused extensive damage, which motivated us to establish a temporary seismic network around the rupture zones of these earthquakes. With the available continuous seismic data recorded from eight seismic stations, we cross correlate the vertical component of ambient-noise records and calculate Rayleigh-wave group velocity dispersion curves for interstation pairs. A genetic algorithm is adopted to fit the averaged dispersion curve and invert a 1D crustal velocity model, which constitutes two layers (upper and lower crust) and a half-space (uppermost mantle). The resulting thickness values for the upper and lower crust are 6.9 and 13.5 km, respectively. The shear-wave velocities (V-S) of the upper crust, lower crust, and uppermost mantle are 2.62, 3.54, and 4: 10 km/s with V-P/V-S ratios of 1.745, 1.749, and 1.766, respectively. The differences between the predicted and observed travel times show that our 1D model (WSOLOCrust) has average 0.85- and 0.16-s improvements in travel-time residuals compared with the global iasp91 and local CRUST 1.0 models, respectively. This layered crustal velocity model for the western Solomon Islands can be further used as a referenced velocity model to locate earthquake and tremor sources as well as to perform 3D seismic tomography in this region. Electronic Supplement: Figures showing the misfit of inversion process and the comparison between observed and synthetics and the location of experiments in previous studies and tables listing information about the seismic network, parameters of the genetic algorithm (GA), information of earthquakes used in this study, and results obtained from different 1D models.
Characterizing the Hsincheng active fault in northern Taiwan using airborne LiDAR data: Detailed geomorphic features and their structural implications
(2007-11-15)
Chan, Yu-Chang
;
Chen, Yue-Gau
;
Shih, Tian-Yuan
;
Huang, Chung
;
土木工程學系
We applied newly acquired high-resolution airborne LiDAR data to study a segment of the Hsincheng fault, a well-known active fault near a large industrial park in northern Taiwan. The Hsincheng fault has received much attention and study in the past; but high spatial resolution digital elevation models have not previously been applied to the study of the fault and its surrounding structures. We processed the acquired LiDAR data and produced I in digital elevation models (DEMs) to investigate the active fault adjacent to the densely populated and important infrastructure in Taiwan. Using the LiDAR DEMs, aerial photographs and topographic maps, we show highly detailed geomorphic characteristics around the study area of the Hsincheng fault. Three major characteristics of the study area are defined that include three very well preserved river terraces at varying levels, the fault/fold scarp of the Hsincheng fault, and meandering river systems. Using the LiDAR DEMs, we were able to detect with precision several fault/fold scarps and very gentle NE-trending folding of the river terraces. In general, the LiDAR DEMs have provided unprecedented clarity of landforms for one segment of the Hsincheng fault, which has helped the characterization of subtle but important geomorphic features. (c) 2007 Elsevier Ltd. All rights reserved.