The Current Crustal Vertical Deformation Features of the Sichuan–Yunnan Region Constrained by Fusing the Leveling Data with the GNSS Data

Yong Zhang,Caijun Xu,Shuang Zhu,Zhijiang Zheng,Hongbao Liang

doi:10.3390/rs14051139

Yong Zhang, Caijun Xu + Show 3 more

Open Access

https://doi.org/10.3390/rs14051139

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Journal: Remote Sensing	Publication Date: Feb 25, 2022
Citations: 1	License type: CC BY 4.0

Affiliation: Wuhan University, China Earthquake Administration

Abstract

This study uses the least squares collocation method to fuse the leveling vertical deformation velocity in the Sichuan–Yunnan region with the GNSS observations of this region from 320 stations in the China Crustal Movement Observation Network (CMONOC) and the China Continental Tectonic Environment Monitoring Network (CMTEMN) from 1999 to 2017. Such fusion is to improve the accuracy of the vertical deformation rates in large spatial scales. The fused vertical deformation results show that: (1) the fused deformation field has a uniform spatial distribution, and shows detailed change characteristics of key regions; (2) the current vertical crustal motion in this region is featured by the contemporaneous occurrence of crustal compression, shortening and uplift and basin extensional subsidence; (3) most areas in this region experience uplifts, as the lateral push of the Qinghai–Tibet Plateau was blocked by the Sichuan Basin. The areas on the northwest side of the Longmenshan fault and the Lijiang-Xiaojinhe fault are dominated by uplifts, with the velocity of 1.5 mm/a–5.5 mm/a, and the region on the southeast side has slight uplifts, with the velocity of 1.0 mm/a–1.5 mm/a; (4) many areas have high gradient vertical deformation, especially the region close to the Wenshan fault and on the two sides of the Yarlung Zangbo fault that has the value of 3.0–4.0 × 10−8/a, deserving further attention to be paid to the long-term earthquake hazards.

Highlights

The Sichuan–Yunnan region (SYR) is located on the southeastern margin of the Qinghai–Tibet Plateau (QTP) in southwestern China, and is the edge of the area bearing the interaction between the Eurasian plate and the Indian plate
The leveling observation increases the spatial density of the GNSS observation across the faults, and the GNSS observation makes the spatial distribution of the leveling observation more even
The vertical crustal movement features in the SYR (Figure 2) suggest that the southeastern margin of the QTP was blocked by the Sichuan Basin, so most of the material flowed southward along the arc-shaped channel into southern Yunnan, some of which was blocked by the Lijiang-Xiaojinhe fault

Summary

Introduction

The Sichuan–Yunnan region (SYR) is located on the southeastern margin of the Qinghai–Tibet Plateau (QTP) in southwestern China, and is the edge of the area bearing the interaction between the Eurasian plate and the Indian plate. QTP, the SYR experienced strong crustal motions, so this region has great topographic fluctuation and frequent seismic activity. The “lower crustal flow mode” [12–15] were developed to constrain the internal deformation and lateral extrusion of the QTP, respectively. Believes that the middle and lower crusts of the QTP are weak, where the crust thickening and shortening on the eastern margin of the plateau are most likely to occur [14,16,17] This model has been widely accepted as it can well explain the crustal deformation characteristics observed on the surface. Some scholars believed that the lower crustal flow from the eastern QTP was blocked by the Lijiang-Xiaojinhe fault and stopped at the northern Yunnan [30]. The rich archive leveling and GNSS observations can be used for studying the crustal vertical deformation characteristics.

Leveling Data

GNSS Data

Fusion of the Leveling Results and the GNSS Results

The Current Vertical Crustal Deformation in the SYR

Kinetic Mechanism

Distribution of Lower Crustal Flows