Early Postseismic Deformation from the 16 October 1999 Mw 7.1 Hector Mine, California, Earthquake as Measured by Survey-Mode GPS

Rapid field deployment of a new type of continuously operating Global Positioning System (GPS) network and data from Southern California Integrated GPS Network (SCIGN) stations that had recently begun operating in the area allow unique observations of the postseismic deformation associated with the 1999 Hector Mine earthquake. Innovative solutions in fieldcraft, devised for the 11 new GPS stations, provide high-quality observations with 1-year time histories on stable monuments at remote sites. We report on our results from processing the postseismic GPS data available from these sites, as well as 8 other SCIGN stations within 80 km of the event (a total of 19 sites).

Section: Temporal Changessupporting

confidence: 87%

Section: Gps Data and Data Processingmentioning

confidence: 99%

Continuous GPS Observations of Postseismic Deformation Following the 16 October 1999 Hector Mine, California, Earthquake (Mw 7.1)

Hudnut¹,

King²,

Galetzka³

et al. 2002

“…Both the Landers and Hector Mine earthquakes initiated robust aftershock sequences, as well as triggering seismicity as far as several hundred kilometers from the rupture plane (Hauksson et al, 2002). Before addressing the relationship between these two earthquakes and the nature of postseismic deformation from the Hector Mine event (e.g., Pollitz et al, 2001;Hudnut et al, 2002;Pollitz and Sacks, 2002;Masterlark and Wang, 2002;Owen et al, 2002), we (Treiman et al, 2002). Solid squares denote ERS radar scenes for the ascending (track 77, frames 675 and 693), and descending (track 127, frames 2907 and 2925) orbits.…”

Section: Introductionmentioning

confidence: 99%

Coseismic Deformation from the 1999 Mw 7.1 Hector Mine, California, Earthquake as Inferred from InSAR and GPS Observations

Simons¹

2002

415

354

We use interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) observations to investigate static deformation due to the 1999 M w 7.1 Hector Mine earthquake, that occurred in the eastern California shear zone. Interferometric decorrelation, phase, and azimuth offset measurements indicate regions of surface and near-surface slip, which we use to constrain the geometry of surface rupture. The inferred geometry is spatially complex, with multiple strands. The southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a N45ЊW direction. The central segment is the simplest, with a single strand crossing the Bullion Mountains and a strike of N10ЊW. The northern third of the rupture zone is characterized by multiple splays, with directions subparallel to strikes in the southern and central. The average strike for the entire rupture is about N30ЊW. The interferograms indicate significant alongstrike variations in strain which are consistent with variations in the ground-based slip measurements. Using a variable resolution data sampling routine to reduce the computational burden, we invert the InSAR and GPS data for the fault geometry and distribution of slip. We compare results from assuming an elastic half-space and a layered elastic space. Results from these two elastic models are similar, although the layered-space model predicts more slip at depth than does the half-space model. The layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km. Contrary to preliminary reports, the northern part of the Hector Mine rupture accommodates the maximum slip. Our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models. The inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake.

“…This situation would be difficult to detect and eliminate based on only a single collection of postearthquake LiDAR data, but we can use GPS observations to help evaluate this. The GPS data collected after the Hector Mine earthquake indicated postseismic velocities consistent with continued right-lateral motion, with the maximum rates decaying from ∼10 cm=yr over the first 30 days to ∼5 cm=yr over the following 130 days Hudnut, King, et al, 2002;Owen et al, 2002). Thus, postearthquake deformation following the mainshock was negligible (less than 10 cm) and would not contribute much to the slip distribution.…”

Section: Comparison Of Horizontal and Vertical Displacements Between mentioning

confidence: 92%

Fault‐Slip Distribution of the 1999M_w 7.1 Hector Mine Earthquake, California, Estimated from Postearthquake Airborne LiDAR Data

Chen¹,

Akciz²,

Hudnut³

et al. 2015

The 16 October 1999 Hector Mine earthquake (M w 7.1) was the first large earthquake for which postearthquake airborne Light Detection and Ranging (LiDAR) data were collected to image the fault surface rupture. 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 displacements using a 0.5 m digital elevation model derived from the LiDAR imagery. The slip measurements based on the LiDAR dataset are highest in the epicentral region, and taper in both directions, consistent with earlier findings by other works. 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 resolving 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 postearthquake airborne LiDAR survey can produce an along-fault horizontal and vertical offset distribution plot of a quality comparable to a reconnaissance field survey. Although LiDAR data can provide a 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 resolve slip that is distributed over several fault strands across a zone. 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.Online Material: Tables of LiDAR displacement measurements; slip distributions plots; Google Earth index files and locations where displacements were made; LiDAR data files, and access information to view screen captures of the displacement measurements.