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Book Chapter

Seismicity of central Italy in the context of the geological history of the Umbria-Marche Apennines

By
Massimiliano R. Barchi
Massimiliano R. Barchi
Dipartimento di Fisica e Geologia, Università di Perugia, 06123 Perugia, Italy
CRUST (Centro Interuniversitario per l’analisi SismoTettonica Tridimensionale con Applicazioni Territoriali), 66100 Chieti, Italy
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;
Cristiano Collettini
Cristiano Collettini
Dipartimento di Scienze della Terra, Sapienza Università di Roma, 00185 Roma, Italy
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Publication history
15 January 201910 May 2019

ABSTRACT

In the Umbria-Marche Apennines, direct evidence of earthquakes (including data from geodetic, geophysical, historical, and paleoseismological research) is not older than 20–10 ka, but the events themselves are influenced by the whole ~250 m.y. geological history of the region. For seismic sequences that have occurred in the past few decades, seismological data of increasing quality provide detailed images of the active NNW-SSE–trending normal fault systems in the upper 10 km of the crust. Major historical earthquakes and sparse paleoseismological data are also aligned parallel to the same lineaments, which clearly define the distribution of the major seismogenic sources of the region. The close connection between active tectonics and older Quaternary faults that border a series of extensional intramountain basins is demonstrated by the fact that seismogenic and Quaternary faults are distributed along the same alignments, formed within similarly oriented stress fields, and accommodate WSW-ENE extension coherently with the active strain field. The Quaternary to present tectonics form part of a long-lived extensional process, active over 15–20 m.y., which is migrating eastward through time across the Italian peninsula, superimposed on the previous compressional phase that created the Apennines. The older Umbria-Marche geological history, recorded in the Triassic to Paleogene stratigraphic succession of the region, also influences the present-day distribution of seismicity. Specifically, the complex mechanical stratigraphy of the region determines the superposition of rocks with different rheological behaviors and overall thickness of the seismogenic layer. Almost all of the earthquakes occur within the sedimentary cover, with main shocks located close to the basal contact with the underlying Paleozoic basement.

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GSA Special Papers

250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco

Geological Society of America
ISBN electronic:
9780813795423

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