Correlazione tra sismicità ed elementi strutturali nell'isola d'Ischia

Abstract

An integrated study on historical seismicity and tectonic structures has made it possible to recognize the relationships between macroseismic data and strain field in the northern part of the island of ischia (Gulf of Naples, Southern Italy). Macroseismic maps based on new data and information from the literature suggest that the epicentral area was probably located in a restricted area that coincides with the northern border of Mt. Epomeo "horsf; this is the most conspicuous morphostructural feature of the island and is thought to control both seismic and tectonic activity in the island. Isoseismal lines have a clear E-W trend; the maximum gradient is oriented N-S and coincides with the least damaged areas. Kinematic analyses of the faults in the volcanic deposits of Casamicciola (a village on the north of Mt. Epomeo), indicate a principal extension along the N to NNE direction in the oldest (> 35 ka) tuffs; a secondary extension and transtension occur along a NNW direction and seem to affect also younger (10*2 ka) pumiceous formations. Both extensional episodes are localized on E-W to WNW-ESE trending structures. Major dip-slip displacements present along the Mt. Epomeo border faults are markedly attenuated to the east, where younger volcanic edifices (< 10 ka) seem to seal most of the deformation structures. This situation conforms to the geometry of isoseismal lines and suggests a possible geneticai Sink between macroseismic and local strain fields, in turn controlled by the regional strain field of Southern Italy.