Long‐term earthquake clustering: A 50,000‐year paleoseismic record in the Dead Sea Graben

Abstract

The temporal distribution of earthquakes in the Dead Sea Graben is studied through a 50,000‐year paleoseismic record recovered in laminated sediments of the Late Pleistocene Lake Lisan (paleo‐Dead Sea). The Lisan represents more than 10 times the 4000 years of historical earthquake records. It is the longest and most complete paleoseismic record along the Dead Sea Transform and possibly the longest continuous record on Earth. It includes unique exposures of seismite beds (earthquake‐induced structures) associated with slip events on syndepositional faults. The seismites are layers consisting of mixtures of fragmented and pulverized laminae. The places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment‐water interface during slip events on these faults. Thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water‐sediment interface on both sides of the fault scarps. Modern analogs and the association with surface ruptures suggest that each seismite formed during an ML ≥ 5.5 earthquake. The 230Th‐234U ages of a columnar section, obtained by thermal ionization mass spectrometry, give a mean recurrence time of ∼1600 years of ML ≥ 5.5 earthquakes in the Dead Sea Graben. The earthquakes cluster in ∼10,000‐year periods separated by quiet periods of similar length. This distribution implies that a long‐term behavior of the Dead Sea Transform should be represented by a mean recurrence of at least 20,000 year record. This observation has ramifications for seismic hazard assessment based on shorter records.

Reading a 400,000-year record of earthquake frequency for an intraplate fault

“…3B). We note that clusters previously documented on plate-bounding faults are generally separated by pronounced periods of quiescence (8)(9)(10)(11)(12). In contrast, our results show that an earthquake cluster may be an anomaly in an otherwise quasiperiodic record, at least on intraplate faults.…”

“…However, an alternative view posits that spatial and temporal variations in fault strength and/or mechanical interactions between adjacent faults can lead to either a random or a clustered distribution of seismic events for a given fault (8)(9)(10)(11)(12)(13). This view has led to greater use of "time-independent" and clustered earthquake recurrence models.…”

Irregular earthquake cycle along the southern Tianshan front, Aksu area, China

“…Similar aperiodic behavior was reported along the Dead Sea Fault zone [Marco et al, 1996]. Other examples of long-term analysis of seismic activity using historical catalogs [Ambraseys, 1989;Vere-Jones and Ozaki, 1982;Xu and Deng, 1996;Goes, 1996], paleoseismologic data [Jacoby et al, 1998;Grant and Sieh, 1995;Marco et al, 1996;Wells et al, 1999], geomorphological data [Ritz et al, 2003], or geodesic and geologic data [Friedrich et al, 2003] show that periods of activity can alternate with periods of quiescence along a single fault or a group of faults and that many fault zones exhibit temporal earthquake clustering [Pirazzoli et al, 1996].…”

“…[3] Historical earthquake records [Ambraseys, 1989;Vere-Jones and Ozaki, 1982;Xu and Deng, 1996;Goes, 1996] and paleoseismologic data [Jacoby et al, 1998;Grant and Sieh, 1995;Marco et al, 1996;Wells et al, 1999] have, however, shown that earthquake recurrence time and earthquake-related slip on a given fault can show great variations. These variations are yet poorly understood though several models predict irregular behavior [Bak and Tang, 1989;Carlson and Langer, 1989;Ben-Zion, 1996;Shaw and Rice, 2000].…”

Acceleration and evolution of faults: An example from the Hunter Mountain–Panamint Valley fault zone, Eastern California

“…However, for other fault zones, discrepancies between geodetic and geologic rates are often observed, and have led to suggestions of complex behavior such as slip pulses, strain waves, and possible relations to earthquake clusters and other non-linear spatial-temporal deformation processes (Meade and Hager, 2005;Marco et al, 1996;Rockwell et al, 2000;Peltzer et al, 2001;Bennett et al, 2004;Friedrich et al, 2004;Oskin and Iriondo, 2004;Dolan et al, 2007;Oskin et al, 2008).…”