The Present-Day Crustal 3D Movement and Geodynamic Mechanisms in Hainan Island

Yaxuan Hu,Shanlan Qin,Jiuchang Hu,Bin Zhao

doi:10.4236/gep.2020.85015

Abstract

The characteristics of the present-day crustal three dimensional (3D) movement with GNSS data during 1999-2018 and the precise leveling data during 1970s-2018 in Hainan Island and its adjacent area are analyzed. Based on the data and the horizontal movement field in the region of Southeast Asia, we discuss how the horizontal velocities in Hainan and the continental margin of the South China block (SCB) are affected by the Eurasian plate, the India-Australia plate and the Philippine Sea plate. The results show the movement of Hainan Island is the same as SCB. The horizontal velocities of the continental margin in South China are different in the east and the west along the boundary of the Northeastern Coast block and Yangtze Block. In Hainan Island, the 3D movement is different in two regions divided by Baisha fault. The movement of SCB is affected by Indo-European collision and extrusion. The movement of the continental margin is affected by both the Pacific Ocean plate, the Philippine Sea plate, the expansion of the South China Sea (SCS), the hot materials underplating and subsequent lithospheric extension. The effect on the regional movement by the Australia plate is smaller, but it can cause co-seismic step to SCB when there had a giant earthquake in Sumatra which is caused by the convergence of the Australia with the Sunda Plate in the NE direction.

Highlights

The results show the movement of Hainan Island is the same as South China block (SCB)
The above analysis reveals that the characteristics of 3D crustal movement in Hainan Island
The movement of SCB is influenced by the Indo-European collision and extrusion, and the continental margin of the block influenced by the Pacific, Philippine and South China Sea (SCS) plate movements

Summary

Introduction

Base on the GNSS data since 1998, the horizontal movement of Hainan and SCB is SEE and the differences of the value of the velocities are small (Li, et al, 2010; Hu et al, 2014; Hu et al, 2016). Based on the precise leveling data during 1950s-1980s, the vertical movement in the north island reveals the different in the two sides of Haikou-TunChang. It was ascending in the east and descending in the west (Zhu, 1988). Time Series of the Baseline Changes The station MALN is located in the center of the GNSS network in the northern island (Figure 3). The baselines of the east stations to MALN are shortened by extrusion and the changes are greater with time. The baselines from MALN to F051, F052 and LEZH, which on the north region are less stretched

Vertical Movement

Baisha Tectonic Belt

Influence of the Surrounding Plates

Conclusion