Interpreting Soft Sediment Deformation and Mass Transport Deposits as Seismites in the Dead Sea Depocenter

Abstract

We have studied the history of earthquakes over the past 70 kyr by analyzing disturbed sedimentary layers around the margins of the Dead Sea. However, we know little about disturbances in the basin depocenter, where water depth is ~300 m, and accessible only by drilling. In this study, we compare disturbances from the Dead Sea depocenter, with the contemporaneous earthquake record (~56–30 ka) that was recovered on the western margin of the lake. This comparison allows us to discern the characteristics of disturbance in the different subaqueous environments and identify the source and sedimentary process of mass transport deposits. Our observations indicate that (i) the long disturbance sequences in the Dead Sea depocenter are composed of in situ deformation, slump, and chaotic deposits; (ii) earthquake‐triggered Kelvin‐Helmholtz Instability is a plausible mechanism for the in situ deformation in the lake center; (iii) the slump is slope area sourced; (iv) the unit of chaotic deposits is lakeshore sourced; and (v) earthquake‐triggered slope instability is a viable mechanism for the slump and chaotic deposits. We further suggest that long sequences of disturbance in seismically active lake depocenters can be used to infer earthquake clusters.

Some features of deformation structures in an esker on the southern margin of the Fennoscandian shield

“…The contributions of these mechanisms can be assessed in different ways. Often earthquakes are triggers (Lu et al, 2017) for further redistribution of sediments. In thic case, earthquakes could have disrupted the wet sediments and initiate the growth of a diapir through the varved clay.…”

Deglacial record of palaeoearthquakes interpreted from mass transport deposits at three lakes near Rouyn‐Noranda, north‐western Quebec, Canada

“…Overall, the lack of convincing aseismic mechanisms implies that palaeoearthquakes are the best explanation for multi‐MTD event horizons within the Duparquet and Dufresnoy study areas, similar to the interpretation by Brooks () at Lac Dasserat. Comparable assessments of seismic and aseismic mechanisms for subaqueous MTDs have been conducted by other studies in different environmental settings (Schnellmann et al ., ; Moernaut et al ., ; Waldmann et al ., ; Lowag et al ., ; Lu et al ., ). The seismogenic interpretation for the multi‐MTD event horizons is also consistent with those made by Doughty et al .…”

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

“…1d-m) (Lu et al, 2017b;Lu et al, 2020b). The first four types of sediment are regarded as background sedimentation (Text S2), whilst disturbed units including soft-sediment deformation, liquefied sand layers, slumps, chaotic deposits, and micro-faults have been interpreted as seismites (Marco and Agnon, 1995;Ken-Tor et al, 2001;Heifetz et al, 2005;Wetzler et al, 2010;Lu et al, 2017b;Lu et al, 2020b).…”

“…Widespread in situ soft-sediment deformation characterizes the Dead Sea sediments (Marco and Agnon, 1995;Lu et al, 2017b;Alsop et al, 2019), which manifests as several forms of (i) linear waves, (ii) asymmetric billows, (iii) coherent vortices, and (iv) intraclast breccias ( Fig. 1d-m) (Lu et al, 2020b).…”

“…Confidential manuscript submitted to Geophysical Research Letters 11 and VII are slump and chaotic deposits without underlying in situ seismites, respectively (Lu et al, 2017b).…”