NSF-BSF: Earthquake temporal occurrence variability (clustering) observed in the longest detailed paleoseismic record: climatic modulation on the tectonic signal

Florida International University, Miami FL

Investigators

Abstract

The Dead Sea Fault (DSF) in Israel provides a unique opportunity to study the long-term history of earthquakes along a major fault: in some places it passes under the Dead Sea, and evidence of past earthquakes is recorded in layers of seafloor sediments. When a large earthquake occurs, the violent shaking deforms the softest shallow sediments, forming “seismites”. Over 200,000 years worth of seismites have been documented in rocks and in core samples taken from a deep drill hole in the Dead Sea. Wdowinski and his Israeli collaborators have discovered an apparent link between earthquakes (as recorded by seismites) and changes in Dead Sea water levels, suggesting that climate variations may affect the timing of earthquakes. In this proposal, they plan to thoroughly to test this hypothesis, using a wide range of methods such as time series analysis, GIS tools, geological mapping, and computer models of fluid flow and fault mechanics. Their findings may help us better understand whether climate change might affect earthquake timing on other fault systems that pass under large lakes or inland seas, such as the southern San Andreas Fault in California. The Israeli and US teams have split up the work so the Israeli scientists do the geological mapping and seismite modeling, and the US scientists model Dead Sea fault mechanics and do mathematical methods to thoroughly test whether DSF earthquakes and water level changes correlate. This is a project jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF-GEO) and the Israel Binational Science Foundation (BSF) in accord with the language in the Memorandum of Understanding between the NSF and the BSF. This Agreement allows a single collaborative proposal, involving US and Israeli investigators, to be submitted and peer-reviewed by NSF. Upon successful results of the NSF merit review and recommendation by the cognizant NSF Program of an award, each Agency funds the proportion of the budget and the investigators associated with its own country. The Dead Sea Fault (DSF) provides a unique opportunity to study long-term temporal variability in earthquake occurrence along a continental transform fault through its detailed paleoseismic record, spanning the past 220,000 years. This record, derived from borehole and outcrop observations of seismites—sediments deformed by earthquake shaking in the lakes of the Dead Sea Basin—reveals a significant correlation between long-term earthquake occurrence and lake levels, suggesting a climatic impact on earthquake frequency. This research investigates the impact of lake level changes on the paleo-earthquake record by evaluating the processes involved in seismite formation, including sedimentary unit build-up, seismic shaking, unit tearing, gravitational sliding, and deposition. Seismic shaking is an end product of complex tectonic processes involving strain accumulation, surface load changes, pore pressure changes, and stress release. The shaking interacts with sedimentary processes to generate seismites. The study incorporates five research components: (1) re-analysis of the 220 ka seismite record; (2) spatial detection analysis to assess the uncertainty of single-core paleo-earthquake event detection; (3) geospatial paleo-bathymetry analysis of sediment availability for turbidite generation at different lake levels; (4) fluid mechanical modeling of sediment rheology and deformation style at varying lake levels; and (5) mechanical modeling of earthquake occurrence on both primary strike-slip and secondary normal faults at different lake levels. These components are addressed using time series analysis, GIS tools for spatial slope stability analysis, numerical fluid mechanic simulations of sediment deformation, and boundary and finite element models to calculate stress evolution along fault systems. The research aims to elucidate the influence of climatic factors on seismic activity in the Dead Sea Basin. The interdisciplinary approach, integrating field geology, geodesy, geophysics, paleoseismology, paleoclimate, and sedimentology, seeks to enhance our understanding of long-term earthquake occurrence variability and the governing physical processes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.