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.

Landslide detection by indices of LiDAR point-cloud density

Abstract: The deliverables of an airborne LiDAR survey usually include all points, ground points, digital surface models (DSM) and digital elevation models (DEM). Indices of point clouds tested in this study include density of all points, density of ground points, density of only returns, and density of multiple returns. Shallow landslides are the most common landslides triggered by torrential rainfalls and explicit fresh scars after rainfall events. Multiple returns in forest area give the possibility of differentiating landslide scars from vegetated lands. Classification results from the indices derived from these four kinds of densities are verified by the result obtained by manual interpretation of the derived nDSM images. The experiment is carried out using the dataset obtained in I-Lan County after Typhoon Kalmaegi on 17 July 2008. The results show that a proper definition of the parameters for the indices is most critical for the detection of shallow landslides.

Inventory, mapping, geomorphic characterization, and validation of deep-setated landslides using sky-view factor visualization: northern, central, and southern taiwan

Abstract: . Extreme rainfall with long-term period plays a principal role in triggering deep-seated landslide around the mountainous area. A well-known typhoon Morakot, the most destructive event occurred in August 2009, battered southern Taiwan and caused severe casualties in Siaolin Village. To reduce the damage and to prevent loss of life resulting from the catastrophic landslide, this study adopted high-resolution topographic data which extracted from airborne LiDAR scanning to interpret both recent and ancient deep-seated landslides in northern, central, and southern Taiwan. Firstly, a relief visualization technique called sky-view factor was utilized to generate the quasi-3D map by overlapping slope gradient, and multiple direction hillshading maps, allowing one to interpret manually detailed landslide topography and assess the hazard potential. The study area of the on-going project covers an area of 17,000 km2. This study recognized main scarp and landslide body in polygon pattern by landslide micro-topography interpretation; it showed more than 700 deep-seated landslides were mapped and located on Central Range and Western foothills in Taiwan. The spatial distribution of deep-seated landslide relates highly to the regional strike of formation, daylight at the toe, river-bank erosion, and drainage density. Additionally, the detrimental geomorphic and topographic features are extracted to evaluate the landslide activity in the future. For a landslide zonation which characterized with sharp scarp and greater deformation rate, it usually may represent higher failure susceptibility. This work also uses the 3-D terrain model created by drone photography and geomorphometric analysis to validate the expert-based landslide susceptibility. Furthermore, the result of the study will contribute updating the national-wide environmental geologic map and provide competent authority to make decisions reducing the geohazard risk.

Helium Isotopic Signature of a Plate Boundary Suture in an Active Arc–Continent Collision

Abstract: We report new noble gas signatures of groundwaters, hot springs, and bedrock samples from two major fault systems that form the plate boundary suture between the Eurasian Plate and the Philippines ...

Geomagnetic characteristics of submarine volcanic area off the coast of northern Taiwan

Abstract: As an active mountain building, Taiwan Island is deduced from the oblique collision between the Eurasian and the Philippine Sea plate, and its northern part and offshore region are under post-collision collapse. The magmatism induced from the post-collision collapse therefore distributes in the northern Taiwan and its offshore area. A series of submarine volcanoes and igneous rock isles are rooted in the area. For investigation of the volcanic and igneous arrangement, we have collected the magnetic data over the past few decades to combine and compile a map of regional magnetic anomalies. A pronounced magnetic high largely dominates the area of most submarine volcanoes and extends eastward, while the adjacent areas to the north and west are lower. To better understand the magnetic features for the submarine volcanic area, the magnetization for an equivalent magnetic layer thickness was calculated. The result shows that a high magnetization concentrated on the SV7 and extends northwestward that could be a magnetic dipole combining with its northeastern low part. To the southward, the submarine volcanoes SV1, SV3-SV6 locate between this high and another low magnetization. We also applied the enhanced analytic signal technique from the same magnetic data to evaluate the magnetic source strength distribution. Except for the SV2, SV5 and SV6, the 0th degree of enhanced analytical signal shows that most signal high concentrated on the submarine volcanic areas. For higher degree of enhanced analytical signal, the highest magnitude focus on the Ks and SV1, and PV, SV3 and SV4 are slightly minor.