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Fault slip distribution of the 1999 Mw 7.1 Hector Mine Earthquake, California, estimated from post-earthquake airborne LiDAR data

Ting Chen, Sinan O. Akciz, Kenneth W. Hudnut, Dongzhou Zhang, & Joann M. Stock

Published February 3, 2015, SCEC Contribution #1973

The 16 October 1999 Hector Mine earthquake (Mw7.1) was the first large earthquake for which post-earthquake airborne LiDAR, collected to image the fault surface rupture, exists. In this work, we present measurements of both vertical and horizontal slip along the entire surface rupture of this earthquake based on airborne LiDAR data acquired in April 2000. We examine the details of the along-fault slip distribution of this earthquake based on 255 horizontal and 85 vertical displacement measurements using a 0.5 m DEM derived from the LiDAR imagery. The measurements based on LiDAR dataset are highest in the epicentral region, and taper in both directions, consistent with earlier findings by other workers. The maximum dextral displacement measured from LiDAR imagery is 6.60 ± 1.10 m, located about 700 m south of the highest field measurement (5.25 ± 0.85 m). Our results also illustrate the difficulty in acquiring displacements smaller than 1 m using LiDAR imagery alone. We analyze slip variation to see if it is affected by rock type, and whether variations are statistically significant. This study demonstrates that a post-earthquake airborne LiDAR survey can produce an along-fault horizontal and vertical offset distribution plot at a quality comparable to a field survey. While LiDAR data can provide higher sampling density and enable rapid data analysis for documenting slip distributions, we find that, relative to field methods, it has a limited ability to quantitatively document distributed and diffuse deformation. We recommend a combined approach that merges field observation with LiDAR analysis, so that the best attributes of both quantitative topographic and geological insight are utilized in concert to make best estimates of offsets and their uncertainties.

Chen, T., Akciz, S. O., Hudnut, K. W., Zhang, D., & Stock, J. M. (2015). Fault slip distribution of the 1999 Mw 7.1 Hector Mine Earthquake, California, estimated from post-earthquake airborne LiDAR data. Bulletin of the Seismological Society of America, 105(2a). doi: 10.1785/0120130108. http://authors.library.caltech.edu/57110/1/0120130108.full.pdf

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