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Strong proximal earthquakes revealed by cosmogenic (super 3) He dating of prehistoric rockfalls, Christchurch, New Zealand

Benjamin H. Mackey and Mark C. Quigley
Strong proximal earthquakes revealed by cosmogenic (super 3) He dating of prehistoric rockfalls, Christchurch, New Zealand
Geology (Boulder) (November 2014) 42 (11): 975-978

Abstract

The 2011 rupture of previously undetected blind faults beneath Christchurch, New Zealand, in moment magnitude (M (sub w) ) 6.2 and 6.0 earthquakes triggered major rockfalls that caused fatalities and infrastructure damage. Here we use field, geospatial, seismologic, numerical modeling, and cosmogenic (super 3) He data to provide first evidence for prehistoric rockfall ca. 8-6 ka, and a possible preceding event ca. 14-13 ka, at a site where extensive rockfall occurred in the Christchurch earthquakes. The long ( approximately 7 + or - 1 k.y.) time intervals between successive rockfall events and the high peak ground velocity thresholds required for rockfall initiation at this site ( approximately 20-30 cm/s) preclude earthquakes from major identified seismic sources, including the plate boundary Alpine fault, as likely rockfall triggering sources. Rockfalls were probably triggered by strong paleo-earthquakes sourced from active faults proximal (i.e., <10-20 km) to Christchurch, including the sources of the 2011 Christchurch earthquakes and/or other currently unidentified faults. Given the inherent incompleteness of seismic source catalogues and challenges in obtaining earthquake chronologies for blind faults, high scientific priority should be given to the search for, and analysis of, geologic records of strong earthquake shaking near populated areas.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 42
Serial Issue: 11
Title: Strong proximal earthquakes revealed by cosmogenic (super 3) He dating of prehistoric rockfalls, Christchurch, New Zealand
Affiliation: University of Canterbury, Department of Geological Sciences, Christchurch, New Zealand
Pages: 975-978
Published: 201411
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2014-105171
Categories: Quaternary geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2014345
Illustration Description: illus. incl. geol. sketch map
S43°32'60" - S43°32'60", E172°40'00" - E172°40'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201452
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