A Paleoseismic Record of Earthquakes for the Dead Sea Transform Fault between the First and Seventh Centuries C.E.: Nonperiodic Behavior of a Plate Boundary Fault (original) (raw)
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Bulletin of The Seismological Society of America, 2011
The continuous record of large surface-rupturing earthquakes along the Dead Sea fault brings unprecedented insights for paleoseismic and archaeoseismic research. In most recent studies, paleoseismic trenching documents the late Holocene faulting activity, while tectonic geomorphology addresses the long-term behavior (> 10 ka), with a tendency to smooth the effect of individual earthquake rupture events (M w > 7). Here, we combine historical, archaeological, and paleoseismic investigations to build a consolidated catalog of destructive surface-rupturing earthquakes for the last 14 ka along the left-lateral Jordan Valley fault segment. The 120km-long fault segment limited to the north and the south by major pull-apart basins (the Hula and the Dead Sea, respectively) is mapped in detail and shows five subsegments with narrow stepovers (width < 3 km). We conducted quantitative geomorphology along the fault, measured more than 20 offset drainages, excavated four trenches at two sites, and investigated archaeological sites with seismic damage in the Jordan Valley. Our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at Tell Saydiyeh, supplemented with a rich historical seismic record, document 12 surface-rupturing events along the fault segment with a mean interval of ∼1160 yr and an average 5 mm=yr slip rate for the last 25 ka. The most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr, with a median value of 790 yr, and suggests an episodic behavior for the Jordan Valley fault. Our study allows a better constraint of the seismic cycle and related short-term variations (late Holocene) versus long-term behavior (Holocene and late Pleistocene) of a major continental transform fault.
The Elat fault (a segment of the Dead Sea Transform) runs along the southern Arava valley (part of the Dead Sea Rift, Israel) forming a complex fault zone that displays a time-dependent seismic behaviour. Paleoseismic evidence shows that this fault zone has generated at least 15 earthquakes of magnitude larger than M 6 during the late Pleistocene and the Holocene. However, at present the Elat fault is one of the quietest segments of the Dead Sea Transform, lacking even microsesimicity. The last event detected in the southern Arava valley occurred in the Avrona playa and was strong enough to have deformed the playa and to change it from a closed basin with internal drainage into an open basin draining to the south.
Geological Society of …, 2002
slip faults. Paleoseismic evidence shows that the Elat fault system has generated at least 15 earthquakes of magnitudes (M) larger than 6 during the late Pleistocene and the Holocene. At least two branches of the fault zone were tectonically active simultaneously, indicating that the seismic response over a period of 80 k.y. was time and space dependent. Late Pleistocene earthquakes displaced the surface by 1-1.5 m; their magnitudes were between M 6.7 and M 7, and their average recurrence interval was 2.8 ؎ 0.7 k.y. Movements along the fault system in the Holocene had a higher frequency and a recurrence interval of 1.2 ؎ 0.3 k.y., but resulted in smaller displacement amounts (0.2-1.3 m) and smaller earthquake magnitudes (M 5.9-M 6.7). Historical records document the last seismic event along the Elat fault zone at ϳ1000 yr ago. The decrease in tectonic activity with time is inferred from the concentration of offset along the fault segments in the central part of the Elat fault zone and the decreased seismicity in the eastern and western margins. The magnitude range determined for the central zone (M 6.1-M 6.7) was likely not high enough to activate the marginal faults. The average slip rate on the normal faults is 0.2 mm/yr. However, the slip rate has changed through time on different fault *E-mail: Rivka@mail.gsi.gov.il. segments in the active wide shear zone and between clusters of events related to the same segment. The event-specific slip rates, therefore, have varied from 0.1 to 0.3 mm/ yr. The decrease in earthquake magnitudes with time, combined with the observations that the last large event occurred in A.D. 1068 and that no microseismicity has been detected during the past 15 yr, might signal locking of the Elat fault zone. This effect, if true, may result from episodic global reorganization of the system's mode of strainenergy release, reflected in the configurational entropy of stress states on the fault. These results have significant implications for seismic hazard assessment in the southern Arava Valley, southern Israel, and underscore the possibility that the Elat fault may be a site of major earthquakes in the near future.
Tectonophysics, 2005
The Elat fault (a segment of the Dead Sea Transform) runs along the southern Arava valley (part of the Dead Sea Rift, Israel) forming a complex fault zone that displays a time-dependent seismic behaviour. Paleoseismic evidence shows that this fault zone has generated at least 15 earthquakes of magnitude larger than M 6 during the late Pleistocene and the Holocene. However, at present the Elat fault is one of the quietest segments of the Dead Sea Transform, lacking even microsesimicity. The last event detected in the southern Arava valley occurred in the Avrona playa and was strong enough to have deformed the playa and to change it from a closed basin with internal drainage into an open basin draining to the south.Paleoseismological, geophysical and archaeological evidences indicate that this event was the historical devastating earthquake, which occurred in 1068 AD in the eastern Mediterranean region. According to the present study this event was strong enough to rupture the surface, reactivate at least two fault branches of the Elat fault and vertically displace the surface and an early Islamic irrigation system by at least 1 m. In addition, the playa area was uplifted between 2.5 and 3 m along the eastern part of the Elat fault shear zone. Such values are compatible with an earthquake magnitude ranging between M 6.6 and 7. Since the average recurrence interval of strong earthquakes during the Holocene along the Elat fault is about 1.2 ± 0.3 ky and the last earthquake occurred more about 1000 years ago, the possibility of a very strong earthquake in this area in the future should be seriously considered in assessing seismic hazards.
The Seismicity along the Dead Sea Fault during the Last 60,000 Years
Bulletin of The Seismological Society of America, 2009
Evidence for unchanging slip rate and a Gutenberg-Richter relation for earthquake distribution along the Dead Sea fault during the past 60,000 yr are presented. The evidence comes from three different segments, approximately 100 km apart, and from three different timescales: prehistoric-paleoseismic, historical, and modern (instrumental) records. The paleoseismic data are based on two different methods. In the southern Arava Valley and the northern Jordan Valley segments, the amount of normal displacement along several faults is used, while in the Dead Sea basin the appearance of brecciated beds, which are considered as seismites, is used. We found that for the southern Arava Valley segment a constant dip-slip rate of 0:5 mm=yr can explain the cumulative normal slip during the past 45,000 yr. This suggests that normal faulting is only ∼10% of the total left-lateral strike-slip motion. We also found that for all three segments, the paleoseismic and historical records of strong earthquakes lie on the linear extrapolation of the frequency-magnitude relation of the instrumental record. The calculated b-values for all three segments are between 0.85 and 1, similar to other major strike-slip faults in the world. It is concluded that the Gutenberg-Richter distribution is a stable mode in the tectonic setting of the Dead Sea fault during the past 60,000 yr. 2020
Pre-Instrumental Earthquakes Along the Dead Sea Rift
The Dead Sea rift offers a wealth of information about pre-instrumental earthquakes. The types of potential archives include historic seismicity, archaeological sites, disturbed beds in lake deposits, rockfalls within caves as well as on free slopes, and displaced marine terraces. The rich historical archive is useful as a key for deciphering the geological archives. Of the geological archives developed for the Dead Sea rift, lake sections stand out due to the long periods covered with high resolution. Lake deposits contain long and potentially continuous archives of the environment, and of earthquakes in particular. The Holocene drop in Dead Sea level, accentuated with a fast anthropogenic drop, have triggered incision and outcrop formation, permitting access and direct investigation of archives. The ongoing analysis of cores from lake drill-holes will augment the continuity of the archive. The historical information spans periods that exceed the seismic cycle of individual fault segments. One of the provoking results of the comparisons of historical versus geological archives of earthquake activity is the significant difference in the apparent length of the earthquake cycle, where prehistorical data indicates long quiescence periods. This suggests that even the long historical record of the Levant does not encompass the full earthquake cycle along the entire Dead Sea fault. This result underscores the significance of paleoseismic research for the understanding of earthquake-fault mechanics and for hazard assessment.
A 48-kyr-long slip rate history for the Jordan Valley segment of the Dead Sea Fault
Earth and Planetary Science Letters, 2007
We investigate the late Quaternary active deformation along the Jordan Valley segment of the left-lateral Dead Sea Fault and provide new insights on the behaviour of major continental faults. The 110-km-long fault segment shows systematic offsets of drainage systems surveyed at three sites along its southern section. The isotopic dating of six paleoclimatic events yields a precise chronology for the onset of six generations of gully incisions at 47.5 ka BP, 37.5 ka BP, 13 ka BP, 9 ka BP, 7 ka BP, and 5 ka BP. Additionally, detailed mapping and reconstructions provide cumulative displacements for 20 dated incisions along the fault trace. The individual amounts of cumulative slip consistently fall into six distinct classes. This yields: i) an average constant slip rate of 4.7 to 5.1 mm/yr for the last 47.5 kyr and ii) a variable slip rate ranging from 3.5 mm/yr to 11 mm/yr over 2-kyr-to 24-kyr-long intervals. Taking into account that the last large earthquake occurred in AD 1033, we infer 3.5 to 5 m of present-day slip deficit which corresponds to a Mw ∼7.4 earthquake along the Jordan Valley fault segment. The timing of cumulative offsets reveals slip rate variations critical to our understanding of the slip deficit and seismic cycle along major continental faults.