Publication Date:
2018-03-12
Description:
Two underground cavities in the Northern Calabria region, the Romito and the San Paolo caves, have
been selected for speleoseismic analysis in order to provide a timeframe for paleoearthquakes which
have shocked the cave sites and the surrounding area. The caves are positioned in a seismogenically
active region, which has been struck by medium to large earthquakes in historical and pre-historic times.
Moreover, frequent instrumentally measured small to moderate seismicity occurs in the area (M 5.6).
We document damaged carbonate cave deposits, including collapsed and broken stalactites, in-situ
severed stalagmites and stalactites, and collapsed bedrock ceilings. Samples were sawed in order to
expose breakages and contacts within the laminae. Sixteen laminae, eight pairs of pre and post event
laminae, were drilled for dating by the UraniumeThorium disequilibrium technique. Three discrete
events were defined by six of the speleoseismites to (I) 7.4e2.9 ka, (II) 9.7e8.2 ka, and (III) 28.4e27.4 ka.
Two additional speleoseismites gave wide age brackets, but are confined to 65.7e18.6 ka, which overlaps
with event III, but might represent additional events. The present speleoseismic work depicts a scenario
of a minimum of three well-constrained strong shaking events in a time span of the past ~28 ky, yielding
a maximum recurrence interval of ~9 ky. In 2012 the area was shaken by a Mw5.2 earthquake that
apparently did not produced damage within the study cavities, suggesting that this size is a lower
magnitude limit for producing permanent effects in the caves deposits. The speleoseismites we studied
collected must have been generated by larger magnitude events, and/or with different epicenter locations.
This study adds medium or large earthquake events, previously lacking, to the historic and
instrumental record. This may contribute to reduction of gaps in the earthquake record and consequently
a more reliable recurrence interval estimate for damaging earthquakes in the region.
Description:
Published
Description:
176-184
Description:
3T. Storia Sismica
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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