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.

Use of centrifuge experiments and discrete element analysis to model the reverse fault slip

Abstract: This study presents a series of physical model tests and numerical simulations using PFC 2D (both with a dip slip angle=60° and a soil bed thickness of 0.2 m in model scale)at the acceleration conditions of 1g, 40g, and 80 g to model reverse faulting. The soil deposits in prototype scale have thicknesses of 0.2 m, 8 m, and 16 m, respectively. This study also investigates the evolution of a surface deformation profile and the propagation of subsurface rupture traces through overlying sand. This study proposes a methodology for calibrating the micromechanical material parameters used in the numerical simulation based on the measured surface settlements of the tested sand bed in the self-weight consolidation stage. The test results show that steeper surface slope on the surface deformation profile, a wider shear band on the major faulting-induced distortion zone, and more faulting appeared in the shallower depths in the 1-g reverse faulting model test than in the tests involving higher-g levels. The surface deformation profile measured from the higher-g physical modeling and that calculated from numerical modeling show good agreement. The width of the shear band obtained from the numerical simulation was slightly wider than that from the physical modeling at the same g-levels and the position of the shear band moved an offset of 15 mm in model scale to the footwall compared with the results of physical modeling.

Hydrogeochemical Anomalies in the Springs of the Chiayi Area in West-central Taiwan as Possible Precursors to Earthquakes

Abstract: Water samples from both hot and artesian springs in Kuantzeling in west-central Taiwan have been collected on a regular basis from July 15, 1999 to the end of August 2001 to measure cation and anion concentrations as a tool to detect major earthquake precursors. The data identify chloride and sulfate ion anomalies few days prior to major quakes and lasting a few days afterward. These anomalies are characterized by increases in Cl- concentrations from 34.9% to 41.2% and 71.5% to 138.1% as well as increases in SO42- concentrations from 232.7% to 276.8% and 100.0% to 155.1% above the means in both hot and artesian springs. The occurrence of these anomalies is probably explained first as stress/strain-induced pressure changes in the subsurface water systems which then generate precursory limited geochemical discharges at the levels of subsurface reservoirs. Therefore, finally leading to the mixing of previously separated subsurface water bodies occurs. This suggests that the hot and artesian springs in the Kuantzeling area are possible ideal sites for recording strain changes serving well as earthquake precursors.