Seismic Imaging Using DAS and Dark Fiber for Basin-Scale Geothermal System Characterization: Preliminary Results From the Imperial Valley Project
Session: Fiber-Optic Seismology II
Type: Oral
Date: 4/23/2021
Presentation Time: 02:00 PM Pacific
Description:
Distributed Acoustic Sensing (DAS) is a relatively new technique that utilizes short pulses of laser light to measure strain or strain-rate at thousands of locations along an optical fiber, effectively transforming fiber optic cables currently part of the telecommunication network into massive distributed arrays of seismometers. Such large-N seismic arrays can be utilized for detecting and locating natural seismic events or imaging at the meter to km scale using ambient noise approaches. Because of their dense spatial sampling, broad bandwidth, and linear extent (~30 km), such measurements can be used to generate high resolution profiles of shear wave velocity as well as surface wave scattering maps that can assist in structural characterization.
We are conducting an evaluation of DAS coupled to dark fiber for basin-scale seismic imaging in the Imperial Valley, CA within the Salton Trough, an on-shore spreading center with high heat flow and abundant geothermal potential. Our goal is both to detect seismicity at a finer scale than existing regional networks and image velocity structures related to the Brawley Seismic Zone (BSZ) and the Imperial Valley Fault, two features associated with existing produced (Brawley) and potential geothermal resources. Our fiber optic array, extending from Calipatria to El Centro, was established in Nov. 2020 and has been continuously recording over a 28 km section (7000 channels) of telecom fiber crossing the Brawley Field. We will present early results from this project including (a) the design, layout, telemetry system, and noise characteristics of the array, (b) a growing catalog of events ranging from M0.7 to M4 recorded on the major faults within our study area, and (c) initial ambient noise results showing surface wave velocity structure for the top kilometer of sediment below the array. We also demonstrate that ambient noise approaches can be generalized to utilize both the existing regional network and the DAS array to improve areal coverage beyond an essentially linear array.
Presenting Author: Jonathan Ajo-Franklin
Student Presenter: No
Authors
Jonathan Ajo-Franklin Presenting Author Corresponding Author ja62@rice.edu Rice University |
Verónica Rodriguez Tribaldos vrodrigueztribaldos@lbl.gov Lawrence Berkeley National Laboratory |
Feng Cheng marscfeng@rice.edu Rice University |
Patrick Dobson pfdobson@lbl.gov Lawrence Berkeley National Laboratory |
Avinash Nayak anayak7@lbl.gov Lawrence Berkeley National Laboratory |
Robert Mellors rmellors@ucsd.edu University of California, San Diego |
Michelle Robertson mcrobertson@lbl.gov Lawrence Berkeley National Laboratory |
Todd Wood tjwood@lbl.gov Lawrence Berkeley National Laboratory |
Cody Rotermund crotermund@es.net Lawrence Berkeley National Laboratory, ESnet |
Bin Dong dbin@lbl.gov Lawrence Berkeley National Laboratory, Berkeley, California, United States |
Kesheng Wu kwu@lbl.gov Lawrence Berkeley National Laboratory, Berkeley, California, United States |
Alex Popescu alexcpopescu@ischool.berkeley.edu University of California, Berkeley, Berkeley, California, United States |
Denisse Templeton templeton4@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Christina Morency morency1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Eric Matzel matzel1@llnl.gov Lawrence Livermore National Laboratory, Livermore, California, United States |
Seismic Imaging Using DAS and Dark Fiber for Basin-Scale Geothermal System Characterization: Preliminary Results From the Imperial Valley Project
Category
Fiber-optic Seismology