Central Geological Survey, MOEA

About: Central Geological Survey, MOEA is a government organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Landslide & Fault (geology). The organization has 68 authors who have published 81 publications receiving 2037 citations. The organization is also known as: Jīngjì Bù Zhōngyāng Dìzhí Diàochá Suǒ.

National airborne LiDAR mapping and examples for applications in deep-seated landslides in Taiwan

Abstract: For the purposes of geohazard study, a national airborne LiDAR mapping program spanning 2010 to 2015 was launched with the aim of simultaneously capturing the territory (36,000km2) by airborne LiDAR and digital imagery. The results include very detailed digital elevation models (DEM) and digital surface models (DSM) of 1m grid and digital aerial photograph of 50 cm grid, as well as an inventory of the geological disastrous features with the acquired LiDAR data and images. In total, 400 deep-seated landslides are obtained in a preliminary interpretation. In this paper, an example in Chasan Tribal Settlement of the large-scaled landslides is selected for validation to further inspected with other geological investigation means. The results of this paper demonstrate the merit of the national airborne LiDAR survey and the effectiveness of simple manual interpretation approach for a census of deep-seated landslides with LiDAR-derived images of various types of enhancement such as shaded relief.

Insights from heterogeneous structures of the 1999 Mw 7.6 Chi-Chi earthquake thrust termination in and near Chushan excavation site, Central Taiwan

Abstract: We describe and analyze the surface and subsurface deformation of the 1999 Chi-Chi earthquake thrust termination of the Chelungpu fault in and near the Chushan excavation site, central Taiwan. In order to minimize damage to engineering structures within a deformation zone and formulate regulations for earthquake fault zones and fault setbacks, one needs to know the characteristics of the deformation zone and the connection between surface and subsurface deformation. The surface deformation zone of high strain induced by the earthquake faulting ranges from 15 to 70 m in width, and characterized by a 0.5 to 2 m high escarpment is much wider in the hanging wall. Exposures in the trench, 40 m long and 10 m deep, excavated across the earthquake ground rupture, show on the one hand the heterogeneous structure of a steep, monocline-like fold. On the other hand, strikingly different surface deformation profiles on either side of the 14 m wide trench, i.e., semiparabola-like and monoclinal, do not reflect in any obvious way the subsurface structure. The analysis of our detailed mapping results along with well logs suggests that the significant width variation of the surface deformation zone is attributed to secondary faults branching from the dominant fault at several tens of meters depth. The surface profile of the escarpment is controlled by the depth of the relevant fault tip, and the subsurface heterogeneous structure formed during at least four earthquakes.

Revealing coseismic displacement and displacement partitioning at the northern end of the 1999 Chi-chi earthquake, central Taiwan, using digital cadastral data

Abstract: The 1999 Chi-Chi, Taiwan, earthquake ( M w 7.6) was the largest earthquake to strike Taiwan in the twentieth century. Its surface rupture extends more than 100 km in a north–south trend. However, the northern end of this surface deformation abruptly terminates at an area between the Tachia river and the Taan river, where a broad pop-up structure with east to northeast strike (quite different from the north–south-striking main thrust) is found. This pop-up structure is composed of several regions of parallel thrusts and back thrusts and total shortening reaches about 9 m. In order to reveal the displacement field in the pop-up structure and slip vectors of branch faults, we use a digital cadastral system with about 17,000 control points to calculate coseismic displacement around the Shihkang area. The digital cadastral system was originally conceived to survey land and building boundaries. The cadastral system affords high-density control points that reach about 2800 points/km 2 , and the accuracy is to within ±11 cm. Outside of the pop-up structure, the horizontal displacements vectors are 8–9 m in about 330°–340°, changing as they pass through the surface rupture. The azimuth of horizontal displacement shows large variation with the azimuth from 360° to 315° and displacement amounts from about 4–8 m inside the pop-up structure. In addition, according to these cadastral data, we found surface ruptures that had not been observed in previous studies that could be of importance to future disaster assessment.