Resolution limits and completeness in earthquake archives: Lessons from the Dead Sea fault (Invited)
Abstract
The archive of strong earthquake along the Dead Sea Fault stems from a multitude of information sources: Off-fault seismites in deposits by lakes that straddled the fault nearly continuously during the last 70 ka, damaged speleothems in caves extending the record to 280 ka, on-fault excavations, written historical accounts, damage in archaeological structures, and modern seismographs. The combined archive is the basis upon which our understanding of seismicity is built. However, none of the recorders is perfect and all archives are subject to missing information. We show how previously unrecognized events can be recovered from the sedimentary records and from the historical-archaeological records. For sedimentary archives (seismites) we consider complete reworking and obliteration of an earthquake record by a subsequent earthquake, in which case we miss the former. We show that careful scrutiny and structural analysis of the inner structure of seismites can potentially reveal two phases of deformation where the second event did not pulverize the previous one. We also analyze the statistics of Lake Lisan’s archive (late Pleistocene), suggesting that we miss ~10% of the records (~3 events). The analysis is verified against the archive of the last two millennia, for which we have historical control. The abundant archaeological sites and wealth of written accounts in the Middle East where literate peoples lived and travelled continuously for about 3 ka also offer excellent earthquake records. The ages of archaeological structures are more accurate and offer better resolution than any known radiometric method; masonry structures provide piercing points typically more precise than geomorphic features. We take advantage of the multi-layer Tel Ateret which was occupied several times for brief periods, and was displaced and offset by several seismic ruptures. Vague historical records of an earthquake match the archaeological findings and seismite records from the Dead Sea corroborate the identifications. These examples suggest that revision and reduction of uncertainty in long earthquake histories is feasible in regions where the number of events allows statistical analysis, ancient fine sediments are exposed, or archaeological sites coincide with fault zones.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.T41C..06A
- Keywords:
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- 8002 STRUCTURAL GEOLOGY / Continental neotectonics;
- 8036 STRUCTURAL GEOLOGY / Paleoseismology;
- 8111 TECTONOPHYSICS / Continental tectonics: strike-slip and transform;
- 8123 TECTONOPHYSICS / Dynamics: seismotectonics