A continuous 13.3-ka record of seismogenic dust events in lacustrine sediments in the eastern Tibetan Plateau

Hanchao Jiang,Xiaolin Ma,Yanhao Li,Wei Shi,Siqi Zhang,Ning Zhong,Gaozhong Nie,Hongyan Xu

doi:10.1038/s41598-017-16027-8

Abstract

Lacustrine sediments on the eastern Tibetan Plateau (TP) contain a wealth of information on local and regional tectonic activity. High-resolution grain-size and magnetic susceptibility measurements were conducted on the 23.4-m-thick Lixian lacustrine sedimentary sequence spanning from 19.3 to 6.0 ka, revealing 70 prehistoric seismic events on the eastern TP. The seismic events caused intermittent increases in source materials that endowed the samples of an individual event layer with a gradual fining trend along the C = M line on a C (one percentile)-M (median diameter) plot. Grain-size distribution and end-member modeling imply that dust particles of <20 μm in size were transported primarily by long-term suspension, while medium to coarse silt and sand were transported primarily by short-term suspension, such as aeolian transport constrained by local topography. Provenance analysis based on U-Pb zircon ages indicates that dust particles generated by earthquakes at Lixian had no effect on dust deposition at Xinmocun and Diaolin, and vice versa. These prehistoric seismic events, revealed by variations in grain size and magnetic susceptibility, thus provide invaluable information on the long-term behavior of local seismic activity.

Highlights

Earthquakes emanating from a seismogenic fault provide a direct measure of the structure and properties of the fault system
There is no basis for further correlation of these continuous seismic events revealed by sedimentary index variations and Soft-sediment deformation (SSD) structures at Lixian with other regional sites; instead they serve primarily as an indicator of local prehistoric fault activity
High-resolution grain-size and magnetic susceptibility measurements were conducted on the Lixian lacustrine sediments in the eastern Tibetan Plateau (TP), revealing 70 seismic events

Summary

Introduction

Earthquakes emanating from a seismogenic fault provide a direct measure of the structure and properties of the fault system This information is commonly acquired through observations from the instrumental and historical earthquake records of a region. It has been proposed that analogous prehistoric events may have exposed fine sediment grains that were carried by aeolian transport to the ancient Diexi Lake, where 26 seismic events during the last deglacial period have been identified based on analyses of rare earth elements (REE), the morphology of quartz grains, and grain-size analysis[8]. Given that landslides can be triggered by relatively small earthquakes (M > 4.0; Keefer27) and that aeolian dust grains can be provided continuously by exposed fine sediments on mountain slopes, the grain-size and magnetic susceptibility records from thick lacustrine sequences may represent a continuous prehistoric record of the long-term seismogenic behavior on the eastern TP

Methods

Findings

Discussion

Conclusion