Observations at a San Jacinto Fault Zone site (Sage Brush Flat) Using a Nodal Seismic High Frequency Array

Monday, 15 December 2014: 9:45 AM
Frank Vernon1, Juan C Reyes1, Malcolm Charles Adan White1, Geoffrey A Davis1, Jon C Meyer1, Valerie J Sahakian1, Nicholas J Mancinelli1, Yehuda Ben-Zion2, Dimitri Zigone2, Cooper Harris2, Xin Liu2, Hongrui Qiu2, Pieter E Share2, Yaman Ozakin2, Dan Hollis3 and Mitchell Barklage4, (1)University of California San Diego, La Jolla, CA, United States, (2)University of Southern California, Los Angeles, CA, United States, (3)Nodal Seismic, San Gabriel, CA, United States, (4)NodalSeismic, Processing Manager, Signal Hill, CA, United States
Between 7 May 2014 and 13 June 2014 we deployed a tight 1108 element array of 10 Hz vertical geophones in a two-dimensional array with 700 meter aperture centered on the Clark Fault of the San Jacinto Fault Zone. The array was designed to make detailed observations of the shallow damage zone, local failure processes and noise properties of the Clark Fault near the Anza seismic gap. The core of the array consisted of a grid organized with 20 rows perpendicular to and centered on the fault trace, each row with 50 sensors at a nominal 10 meter interstation spacing. The spacing between rows was nominally 30 meters. The remaining 108 sensors were deployed as extensions to multiple rows providing a maximum 700 meter aperture. Each sensor was surveyed using a Real Time Kinematic (RTK) GPS system to an accuracy of approximately 30 cm. The RTK survey was enabled via ad-hoc networking using HPWREN. We will present observations of earthquakes with magnitudes -1 < M < 4 with hypocentral distances ranging from right below the array out to 100 kilometers, along with prosperities of local structures and noise characteristics.