Slip in the 2010–2011 Canterbury earthquakes, New Zealand

Abstract

The 3rd September 2010 Mw 7.1 Darfield and 21st February 2011 Mw 6.3 Christchurch (New Zealand) earthquakes occurred on previously unknown faults. We use InSAR ground displacements, SAR amplitude offsets, field mapping, aerial photographs, satellite optical imagery, a LiDAR DEM and teleseismic body‐wave modeling to constrain the pattern of faulting in these earthquakes. The InSAR measurements reveal slip on multiple strike‐slip segments and secondary reverse faults associated with the Darfield main shock. Fault orientations are consistent with those expected from the GPS‐derived strain field. The InSAR line‐of‐sight displacement field indicates the main fault rupture is about 45 km long, and is confined largely to the upper 10 km of the crust. Slip on the individual fault segments of up to 8 m at 4 km depth indicate stress drops of 6–10 MPa. In each event, rupture initiated on a reverse fault segment, before continuing onto a strike‐slip segment. The non‐double couple seismological moment tensors for each event are matched well by the sum of double couple equivalent moment tensors for fault slip determined by InSAR. The slip distributions derived from InSAR observations of both the Darfield and Christchurch events show a 15‐km‐long gap in fault slip south‐west of Christchurch, which may present a continuing seismic hazard if a further unknown fault structure of significant size should exist there.

Evolution of the 2010–2012 Canterbury earthquake sequence

“…Both geodetic Beavan et al 2012) and seismological models indicate that most of the displacement was very shallow, and was mainly confined to the upper c. 5 km. Fault models developed from the inversion of InSAR measurements indicate slip on some of the fault segments reached 8 m at 4 km depth, indicating large stress drops of c. 10 MPa (Elliott et al 2012), while aftershock relocations by Syracuse et al (2012) along the central Greendale Fault segment indicate event depths from 5.9 to 14 km, mainly several kilometres below the regions of highest slip inferred by Beavan et al (2010).…”

“…6 shows the epicentres of aftershocks in the area between Lincoln and Hornby, as well as moment tensor solutions for two of the larger (M L 5) events that occurred following the 22 February and 13 June 2011 earthquakes. One concern is that significant moment release has still not occurred in this region, in spite of continued aftershock activity (Beavan et al 2012;Elliott et al, 2012). The sense of faulting suggested by the most recent M 5 events suggests a degree of northÁ northwestÁsouthÁsoutheast sinistral faulting, which would indicate short fault segments that may not be capable of hosting larger earthquakes, although right-lateral strike-slip faulting is likely towards the western edge of the Port Hills.…”

The 2011 Mw 7.1 Van (Eastern Turkey) earthquake

“…The methodology used to generate the interferograms, downsample the interferogram, data and determine the fault geometry assuming uniform slip is described by Wright et al [2004] and Elliott et al [2012]. From this result, we subdivide the segments into an array of subfaults following the method outlined by Funning et al [2005] to form a distributed slip model.…”

Coseismic and Postseismic Displacement of 2011 Mw 6.8 Tarlay Earthquake, Myanmar using InSAR Techniques and Inversion Analysis

“…Nevertheless, with the currently available data, we cannot explain with certainty the large differences in the segment from kilometer 10-13 and from kilometer 24-26. On the other hand there is a well-agreed segment of kilometer 14-16 and another segment with relatively small differences from kilometer [16][17][18][19][20][21][22]. Further work such as seismic slip inversion could provide independent validation of our result.…”

“…In both events, the coseismic movements have been measured by ALOS PALSAR. The more details on Darfield earthquake which ruptured a complex set of strike-slip and secondary reverse faults can be found in [16].…”