A New Approach to Constrain the Seismic Origin for Prehistoric Turbidites as Applied to the Dead Sea Basin

Yin Lu,Michael Strasser,G Ian Alsop,Shmuel Marco,Amotz Agnon,Nicolas Waldmann,Nadav Wetzler,Revital Bookman,Jasper Moernaut,Aurélia Hubert‐Ferrari

doi:10.1029/2020gl090947

Abstract

AbstractThe seismic origin of turbidites is verified either by correlating such layers to historic earthquakes, or by demonstrating their synchronous deposition in widely spaced, isolated depocenters. A historic correlation could thus constrain the seismic intensity required for triggering turbidites. However, historic calibration is not applicable to prehistoric turbidites. In addition, the synchronous deposition of turbidites is difficult to test if only one deep core is drilled in a depocenter. Here, we propose a new approach that involves analyzing the underlying in situ deformations of prehistoric turbidites, as recorded in a 457 m‐long core from the Dead Sea center, to establish their seismic origin. These in situ deformations have been verified as seismites and could thus authenticate the trigger for each overlying turbidite. Moreover, our high‐resolution chemical and sedimentological data validate a previous hypothesis that soft‐sediment deformation in the Dead Sea formed at the sediment‐water interface.

Highlights

IntroductionSeismogenic turbidites are commonly used to derive information such as location, timing, intensity and recurrence intervals of paleoearthquakes, and are vital for geohazard assessment (Goldfinger et al, 2003; St-Onge et al, 2004; Gràcia et al, 2010; Polonia et al, 2013; Strasser et al, 2013; Pouderoux et al, 2014; Ratzov et al, 2015; Moernaut et al, 2018; Hubert-Ferrari et al, 2020)
We propose a new approach that involves analyzing the underlying in situ deformations of prehistoric turbidites, as recorded in a 457 m-long core from the Dead Sea center, to establish their seismic origin
Our high-resolution chemical and sedimentological data validate a previous hypothesis that soft-sediment deformation in the Dead Sea formed at the sediment-water interface

Summary

Introduction

Seismogenic turbidites are commonly used to derive information such as location, timing, intensity and recurrence intervals of paleoearthquakes, and are vital for geohazard assessment (Goldfinger et al, 2003; St-Onge et al, 2004; Gràcia et al, 2010; Polonia et al, 2013; Strasser et al, 2013; Pouderoux et al, 2014; Ratzov et al, 2015; Moernaut et al, 2018; Hubert-Ferrari et al, 2020). The use of turbidites as an earthquake indicator requires a demonstration that seismicity is the most plausible trigger, rather than non-seismic factors such as flash floods (Talling et al, 2013; Katz et al, 2015), exceptional discharge (Clare et al, 2016), and storm waves (Paull et al, 2018) This challenge is generally overcome by correlating turbidites with historic earthquakes in a region (Gràcia et al, 2010; Moernaut et al, 2014; Polonia et al, 2016; Wilhelm et al, 2016) or by demonstrating their synchronous deposition in widely spaced, isolated depocenters (Goldfinger et al, 2007; Ratzov et al, 2015; Kioka et al, 2019). The observed deformations in the lake center are similar to seismically induced deformations seen in lakes from other tectonically active regions such as California (Sims, 1973), Anatolia (Avşar et al, 2016), and Southern Italy (Moretti & Sabato, 2007; Vitale et al, 2019)

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