The September 4, 2010, Darfield, New Zealand earthquake is the most damaging earthquake to strike New Zealand since the 1931 Napier Earthquake. Although no lives were lost, damage was extensive in the area, particularly in nearby Christchurch, and economic losses are expected to total over NZ $2 billion. The earthquake is also scientifically interesting and in many ways surprising. It occurred on a previously unmapped fault in an area that was presumed to have lower risks than other areas (e.g., the Alpine Fault). The complex source time function indicates that two or more subevents were involved.One of the most surprising aspects is the predominantly strike-slip character of the event along a nearly east-west fault. South Island tectonics are dominated by the Alpine Fault system and nearby, mostly northeast-southwest striking strike slip faults, such as the Hope Fault. The data from this project will provide a unique opportunity to study a fault that is very likely quite young and immature, and thus fundamentally different in character from mature faults such as the San Andreas Fault in California or the Anatolian Fault in Turkey.
New Zealand and UW-Madison scientists have deployed temporary seismic instruments to monitor aftershocks. The New Zealand instruments were deployed by GNS Science and Victoria University staff, led by Terry Webb and Martha Savage, respectively. PI Thurber arranged for the shipment of 9 RAMP instruments from the IRIS/PASSCAL facility to Christchurch and sent 2 UW-Madison staff to New Zealand to deploy them. 18 short-period, 9 broadband, and 3 strong motion instruments will be deployed through this joint endeavor. The RAMP deployment will continue until mid January 2011. The data will be made available to the scientific community within the time frame required for IRIS/PASSCAL "RAMP" deployments.
The project will support a postdoctoral student to participate in the deployment, and foster a collaboration with scientific teams in New Zealand. This work is jointly supported by the Office of International Science and Engineering and the Geophysics program.
Through National Science Foundation RAPID grant EAR-1102767, nine broadband PASSCAL seismometers were deployed in the area of the Christchurch earthquake rupture zone between September 18 and September 20, 2010. This was a joint effort by two University of Wisconsin-Madison staff and a staff member and two graduate students from Victoria University of Wellington. The instruments were deployed within ~55 km of the surface rupture of the Darfield earthquake and three were installed within 10 m of the surface rupture. The majority of the instruments ran through late December 2011 or early-to-mid January 2011, although one instrument failed in late November 2010. This, in combination with four temporary Victoria University of Wellington instruments and three permanent GeoNet instruments, provides dense coverage of four months of the aftershock sequence of the Darfield earthquake at a station spacing of less than 30 km. Based on the GeoNet catalog, the temporary network recorded over 2100 M2+ aftershocks, including the December 26, 2010 M4.9 Boxing Day earthquake near Christchurch. Since the instruments were removed, the raw data have been processed and the waveforms and station information have been sent to the IRIS DMC, where they are now publicly available under the network code of "4A".
