Distinct lake sedimentary imprints of earthquakes, floods and human activities in the Xiaojiang Fault zone: Towards a quantitative paleoseismograph in the southeastern Tibetan Plateau

Jiawei Fan; Dayou Zhai; Hongyan Xu; Xiaotong Wei; Changfei Jin; Hanchao Jiang; Wei Shi; Xingqi Liu

doi:10.1016/j.scitotenv.2023.161662

Distinct lake sedimentary imprints of earthquakes, floods and human activities in the Xiaojiang Fault zone: Towards a quantitative paleoseismograph in the southeastern Tibetan Plateau

Sci Total Environ. 2023 Apr 10:868:161662. doi: 10.1016/j.scitotenv.2023.161662. Epub 2023 Jan 18.

Authors

Jiawei Fan¹, Dayou Zhai², Hongyan Xu³, Xiaotong Wei⁴, Changfei Jin², Hanchao Jiang⁵, Wei Shi⁴, Xingqi Liu⁶

Affiliations

¹ State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China; Xinjiang Pamir Intracontinental Subduction National Observation and Research Station, Beijing 100029, China; Urumqi Institute of Central Asia Earthquake, China Earthquake Administration, Urumqi 830011, China. Electronic address: jwfan@ies.ac.cn.
² Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650500, China; MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650500, China.
³ State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China. Electronic address: xuhongyan@ies.ac.cn.
⁴ State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China.
⁵ State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China; Xinjiang Pamir Intracontinental Subduction National Observation and Research Station, Beijing 100029, China; Urumqi Institute of Central Asia Earthquake, China Earthquake Administration, Urumqi 830011, China.
⁶ College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China.

PMID: 36681332
DOI: 10.1016/j.scitotenv.2023.161662

Abstract

Lake sediments that widely distributed in the active and complicated fault zones have been recently showing great potential for paleoseismic reconstruction. However, flood events and human activities may make the seismic signal unrecognizable. In this study, high-resolution analyses of sedimentary structure, physical and chemical proxies, as well as absolutely radioactive dating were conducted on seven representative sediment cores from the depocenter, nearshore and inlet areas of Yangzong Lake, a typical fault lake in the Xiaojiang Fault zone, southeastern Tibetan Plateau (TP). These new data were calibrated by historical documents, suggesting that seismically induced mass-transport deposits (MTDs, i.e., turbidites) were massive and/or amalgamated (earthquake doublet), became fining and thickening towards the lake center (without changing lake morphology), and occasionally exhibited soft sediment deformation structures (SSDs, i.e., microfaults). These sediments were relatively poorly sorted and instantaneously deposited from slope failures within the lake. An extremely strong earthquake could cause coseismic subsidence of the lake basin and destruct the local hydrological system, resulting in exceptionally high Mn and total inorganic carbon (TIC) contents in the lake center. In contrast, flood deposits were thinner with horizontal beddings, had higher terrestrial organic matter (higher C/N ratios), and distributed locally in the lake inlet area. Human activities-induced sediments were inversely graded, poorly sorted and gradually deposited, had horizontal beddings and no erosive base, and exhibited high carbon, Pb and Zn contents and low C/N ratios. In addition, macroseismic investigations and statistical results from intensity prediction equations (IPEs) provided a conservative threshold of ∼8 Modified Mercalli Intensities (MMI) for triggering turbidites, and a ∼ 10 MMI for inducing coseismic subsidence and hydrological destruction. This study was among the first attempts to establish a quantitative lacustrine paleoseismograph in the southeastern TP, and the new results would greatly improve the valid assessment of geohazard risks.

Keywords: Anthropocene; Carbon sequestration; Hydrological destruction; Lake paleoseismology; Tibetan Plateau; Turbidite.