Publication Date:
2017-04-04
Description:
To contribute to the understanding of the relationships between moderate earthquakes
and the faults that are recognizable in the geological record, we analysed seismological
and geological data related to the 1997–1998 Umbria-Marche (Central Italy) earthquake
swarm. The seismological recordings, collected by local networks, allowed accurate
location of about 1000 events, whereas the geological field observations provided a picture
of the structural features and the ground-surface deformations. We also re-examined
and used some published data and results, mostly about the fault plane solutions and
the geology.
On the basis of earthquake locations, fault plane solutions, and geological mapping
we explored the possible correlation between the earthquake causative fault planes and
the normal faults exposed in the area. Our results show that the two main shocks that
occurred on 1997 September 26 (MW=5.7 and MW=6.0) originated on the same
structure, reactivating at depth the Colfiorito normal faults. Neither rupture propagated
up to the ground surface, but both triggered gravitational sliding that occurred along
pre-existing fault scarps. The earthquake that occurred on 1997 October 14 (MW=5.6)
originated on another fault branch at a much shallower depth. In spite of its lower
magnitude, this earthquake produced tectonic ruptures where the fault plane projects
to the surface in an area where no faults were previously mapped.
By comparing the palaeostress reconstruction, based on slickenside lineation analysis,
and the focal mechanism solutions, we suggest a possible correlation between the longterm
(Early Middle Pleistocene) cumulative effects of the Colfiorito Fault System
and the short-term behaviour of the fault planes observed during this earthquake
swarm, favouring the idea of a seismogenic source producing clustered moderate-size
earthquakes rather than large events scattered in time.
Description:
ING, SSN, IRTR-CNR
Description:
Published
Description:
214-252
Description:
partially_open
Keywords:
earthquake
;
normal faulting
;
seismotectonics
;
04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
;
04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
;
05. General::05.02. Data dissemination::05.02.02. Seismological data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
1006904 bytes
Format:
application/pdf
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