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Repeated folding during late Holocene earthquakes on the La Cal thrust fault near Mendoza City (Argentina)

Eric Salomon, Silke Schmidt, Ralf Hetzel, Francisco Mingorance and Andrea Hampel
Repeated folding during late Holocene earthquakes on the La Cal thrust fault near Mendoza City (Argentina)
Bulletin of the Seismological Society of America (April 2013) 103 (2A): 936-949

Abstract

In 1861, one of the most destructive earthquakes in the history of Argentina destroyed the city of Mendoza (currently 1 million inhabitants). The magnitude M (sub S) approximately 7.0 earthquake is inferred to have occurred on the 31-km-long La Cal thrust fault, which extends from Mendoza to the north, where it offsets an alluvial fan and small inset terraces along a well-preserved fault scarp. A trench excavated on a terrace that is vertically offset by approximately 2.5 m exposes two main stratigraphic units separated by an erosional unconformity. The coarse-grained upper unit is deformed by three east-vergent folds (F (sub 1) -F (sub 3) ). Retrodeformation of these folds yields total displacements of approximately 2.0 m, approximately 2.4 m, and approximately 0.5 m on the underlying fault splays, respectively. The displacement of approximately 2.0 m recorded by fold F (sub 1) is interpreted as the result of the fault rupture that caused the 1861 earthquake. F (sub 2) and F (sub 3) were presumably generated during the penultimate event with an inferred magnitude of M (sub w) approximately 7.0, although formation during two distinct ruptures cannot be excluded. Finite-element modeling shows that coseismic folding above the tip of a blind thrust fault is a physically plausible mechanism to generate these folds. A published luminescence age of 770+ or -76 years, which is interpreted to date the formation of the deformed terrace, indicates that the two (or possibly three) scarp-forming events occurred during the last approximately 800 years. The fine-grained sediments below the erosional unconformity--that contain evidence for at least one older earthquake--are dated at approximately 12 kyr. Our results indicate that elastic strain energy, which is accumulating at the front of the Precordillera today as shown by Global Positioning System (GPS) data, was repeatedly released during earthquakes on the La Cal fault in the past. Hence, the La Cal thrust fault poses a serious threat to the city of Mendoza.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 103
Serial Issue: 2A
Title: Repeated folding during late Holocene earthquakes on the La Cal thrust fault near Mendoza City (Argentina)
Affiliation: Universitaet Muenster, Institut fuer Geologie und Palaeontologie, Westfaelische Wilhelms, Munster, Germany
Pages: 936-949
Published: 201304
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 58
Accession Number: 2013-035183
Categories: Structural geologySeismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, sects., geol. sketch maps
S38°00'00" - S33°00'00", W71°00'00" - W66°00'00"
Secondary Affiliation: Universidad Nacional de Cuyo, ARG, ArgentinaLeibniz Universitaet Hannover, DEU, Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201322
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