Chyi Tyi Lee

Bio: Chyi Tyi Lee is an academic researcher from National Central University. The author has contributed to research in topics: Landslide & Fault (geology). The author has an hindex of 27, co-authored 64 publications receiving 2715 citations. Previous affiliations of Chyi Tyi Lee include Central University, India & Centre national de la recherche scientifique.

The Chi‐Chi, Taiwan earthquake: Large surface displacements on an inland thrust fault

Abstract: In the early morning (01:47 local time) of September 21, 1999, the largest earthquake of the century in Taiwan (Mw=7.6, ML=7.3) struck the central island near the small town of Chi-Chi. The hypocenter was located by the Central Weather Bureau Seismological Center at 23.87°N, 120.75°E, with a depth of about 7 km. There were extensive surface ruptures for about 85 km along the Chelungpu fault with vertical thrust and left lateral strike-slip offsets. The maximum displacement of about 9.8 meters is among the largest fault movements ever measured for modern earthquakes. There was severe destruction in the towns of Chungliao, Nantou,Taichung, FengYuan, and Tungshi, with over 2300 fatalities and 8700 injuries.

Ground-Motion Attenuation Relationships for Subduction-Zone Earthquakes in Northeastern Taiwan

Abstract: Subduction zone earthquakes have not been taken into special consid- eration in most previous probabilistic seismic hazard analyses (PSHA) in Taiwan. However, they may be critical to properly analyze the earthquake hazard in metro- politan Taipei, so they need to be studied. Strong-motion data from subduction zone earthquakes, of both interface and intraslab types, obtained by the TSMIP and SMART1 arrays in northeastern Taiwan, are used to establish the attenuation equa- tions for peak ground acceleration (PGA) and response spectral acceleration (SA). The resultant PGA and SA attenuation equations include two site classes and two earth- quake source types. The ground-motion values predicted by these attenuation equa- tions are higher than those obtained from the crustal earthquake attenuation equations previously used in Taiwan but are lower than those predicted by the attenuation equa- tions for worldwide subduction zone earthquakes.

Slab breakoff as a mechanism for flipping of subduction polarity in Taiwan

Abstract: We propose a model that involves breakoff of the east-dipping Eurasian slab beneath the Taiwan orogen to account for the flipping of subduction polarity in northern Taiwan. The breakoff was initiated in southern Ryukyu in the early Pliocene and then propagated southwestward into Taiwan, like an opening zipper. Detachment of the Eurasian slab has created a mantle window for the north-dipping Philippine Sea plate to move in laterally, causing a switch in the subduction polarity. Slab breakoff not only provides a testable model for the lithospheric structure of Taiwan, but also accounts for the high heat flow, rapid uplift, synorogenic extension, deep-focus earthquakes, and north-diminishing crustal contraction in the Taiwan mountain belt.

Use of LIDAR in landslide investigations: a review

Abstract: This paper presents a short history of the appraisal of laser scanner technologies in geosciences used for imaging relief by high-resolution digital elevation models (HRDEMs) or 3D models. A general overview of light detection and ranging (LIDAR) techniques applied to landslides is given, followed by a review of different applications of LIDAR for landslide, rockfall and debris-flow. These applications are classified as: (1) Detection and characterization of mass movements; (2) Hazard assessment and susceptibility mapping; (3) Modelling; (4) Monitoring. This review emphasizes how LIDAR-derived HRDEMs can be used to investigate any type of landslides. It is clear that such HRDEMs are not yet a common tool for landslides investigations, but this technique has opened new domains of applications that still have to be developed.

NGA Project Strong-Motion Database

Abstract: A key component of the NGA research project was the development of a strong-motion database with improved quality and content that could be used for ground-motion research as well as for engineering practice. Development of the NGA database was executed through the Lifelines program of the PEER Center with contributions from several research organizations and many individuals in the engineering and seismological communities. Currently, the data set consists of 3551 publicly available multi-component records from 173 shallow crustal earthquakes, ranging in magnitude from 4.2 to 7.9. Each acceleration time series has been corrected and filtered, and pseudo absolute spectral acceleration at multiple damping levels has been computed for each of the 3 components of the acceleration time series. The lowest limit of usable spectral frequency was determined based on the type of filter and the filter corner frequency. For NGA model development, the two horizontal acceleration components were further rotated to form the orientationindependent measure of horizontal ground motion (GMRotI50). In addition to the ground-motion parameters, a large and comprehensive list of metadata characterizing the recording conditions of each record was also developed. NGA data have been systematically checked and reviewed by experts and NGA developers. DOI: 10.1193/1.2894831

Topographic Slope as a Proxy for Seismic Site Conditions and Amplification

Abstract: We describe a technique to derive first-order site condition maps directly from topographic data. For calibration, we use global 30 arc sec topographic data and V S 30 measurements (here V S 30 , refers to the average shear-velocity down to 30 m) aggregated from several studies in the U.S., as well as in Taiwan, Italy, and Australia. V S 30 values are correlated against topographic slope to develop two sets of parameters for deriving V S 30 : one for active tectonic regions where topographic relief is high, and one for stable shields where topography is more subdued. By taking the gradient of the topography and choosing ranges of slope that maximize the correlation with shallow shear-velocity observations, we can recover, to first order, many of the spatially varying features of sitecondition maps developed for California. Our site-condition map for the low-relief Mississippi Embayment also predicts the bulk of the V S 30 observations in that region despite rather low slope ranges. We find that maps derived from the slope of the topography is often well correlated with other independently-derived, regional-scale site-condition maps, but the latter maps vary in quality and continuity, and subsequently, also in their ability to match observed V S 30 measurements contained therein. Alternatively, the slope-based method provides a simple approach to uniform site condition mapping.