GiT-based structural geologic feature analysis of the southern segment of Longmenshan fault zone for earthquake evidence

01/05/2016

Abstract The Longmenshan fault is a thrust fault which runs along the base of the Longmen Mountains in Sichuan province, southwestern China. The southern segment of the fault had two distinct responses to the Ms 8 Wenchuan and Ms 7 Lushan earthquakes. This study determines characteristics of the structural geology of the Longmenshan fault to evaluate how it influenced the two aforementioned earthquakes. This research was done within a Geo-information Technologies (GiT) environment based on multi-source remote sensing and crustal movement data extracted from the Global Positioning System (GPS). The spatial distribution of the southern segment of the Longmenshan fault zone was comprehensively analyzed to study both earthquakes. The study revealed that the Wenchuan and Lushan earthquakes occurred on two relatively independent faults. In addition, there was a nearly constant-velocity crustal movement zone between the two epicenters that probably had a compressive stress with slow motion. Furthermore, the central fault and a mountain back fault gradually merged from north to south. The Lushan earthquake was not an aftershock of the Wenchuan earthquake. The research showed that fault zones within 30–50 km of State Highway 318 are intensive and complex. In addition, crustal movement velocity decreased rapidly, with a strong multi-directional shear zone. Thus, activity in that zone was likely stronger than in the northern part over the medium to long term.