SCEC Award Number 13151 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Renewed Investigation of the Hector Mine Earthquake Surface Rupture with multi temporal field and LiDAR data
Investigator(s)
Name Organization
Joann Stock California Institute of Technology Sinan Akciz University of California, Los Angeles
Other Participants Ken Hudnut, Frank Sousa
SCEC Priorities 4b, 4c SCEC Groups Geology, FARM
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 We conducted new field and computer based investigation of the surface rupture of the October 16, 1999 Hector Mine Earthquake, under SCEC proposal numbers 12188 and 13151 (2012 and 2013). Our field research effort was focused along the ~8 km long maximum slip zone of the rupture, roughly corresponding to the zone of >4 m dextral offset. Our investigation included 1) walking this section of the fault and making measurements of dextral slip while photo documenting the current state of the rupture; 2) creating a difference raster for the entire 8 km maximum slip zone from exactly congruent DEM’s made from years 2000 and 2012 LiDAR data sets; 3) documenting the fault traces with a Trimble GeoXH high precision handheld GPS unit ( /- 10 cm); 4) carrying out field checks of a small number of computer-based offset measurements made using the 2000 LiDAR dataset; and 5) high-resolution low-altitude (<100 m AGL) photography of the maximum slip zone during a helicopter overflight. Important results include 1) identification of two new maximum slip locations where features are offset 7.9 m /- 0.5 m and 6.7 m /- 0.5 m; 2) a database of >30 offset measurements (georeferenced and photo documented) made by our team on the ground; 3) clear changes in fracture visibility in the field, with some fractures more visible, and others no longer visible, compared to the 1999-2000 studies; and 4) examples of a few field checks that both strongly agree and disagree with computer based LiDAR offset measurements.
Intellectual Merit SCEC funded us in 2012 and 2013 for comparative analysis of the two LiDAR data sets and field work along the rupture of the Mw 7.1 Hector Mine earthquake. Analysis of the LiDAR data collected along the rupture in the year 2000 (Hudnut et al, 2002; Zhang et al., 2010; Chen et al., 2013) had three main contributions to a better understanding of this rupture: (1) it increased the spatial density of horizontal displacements, (2) it suggested a new location and larger magnitude of the maximum lateral slip, and (3) it documented rapid slip variations along geometrically simple sections of the fault. In May 2012 a new LiDAR dataset was collected by NCALM under a data-only seed grant to Caltech graduate student Francis Sousa. This covered a significantly broader swath along the same length of the fault. Together these two LiDAR datasets (Fig. 1) comprise a complete, high resolution documentation of this major earthquake surface rupture and show the geomorphic evolution of the rupture in a period of 12 years. As part of his no-cost collaboration, Hudnut of the USGS was able to recover archived data from tapes to provide aerial photography taken in April 2000 after the earthquake, which had not previously been used to interpret the fault features. He also acquired new, very high resolution (1 cm pixel) georeferenced oblique aerial photos in Dec. 2012 along the ~12 km section that had slip of 4 meters or more in 1999.
Broader Impacts Graduate student Frank Sousa was trained in LiDAR data processing, production and differencing of DEMS, and field observations of active faults. Sousa also was trained in presenting his research results at conferences in 2012-2013 (Sousa et al., 2012a and 2012b, 2013a, 2013b), and in helping to write proposals. Graduate student Janet Harvey was trained in field observations of active faults. The LiDAR data set produced by this study will be made available on the OpenTopography web site. The aerial photos shot over the fault zone will be made available on a public web site of the USGS after approval from the US Marine Corps public relations office at 29 Palms US Marine Corps Air-Ground Combat Center.
Exemplary Figure Figure 3. Field measurements made by our team on top of reported yield measurement from the direct aftermath of the earthquake (e.g. Treiman et al, 2002) and computer based measurements made using DEM’s derived from the April 2000 LiDAR scan (Chen et al, in review, Hudnut et al, 2002). Highlighted in gray is the maximum slip zone (~ >4 m r.l. offset) where we focused our efforts during the 2012 field campaign. Note the significant increase in the maximum dextral slip reported here (RCN 11 site shown in Figure 2, plus other sites such as ARMORY, HSZ 6), which concur with further increase maximum offset beyond reported maximum offset of Chen et al, in review. Figure was produced by Frank Sousa by modifying a base figure from Chen et al., in review.