Coda Amplitude Measurements Using Distributed Acoustic Sensing (DAS) Data

Session: Photonic Seismology
Type: Oral
Date: 4/30/2020
Time: 09:15 AM
Room: 215 + 220
Description: 

During a geothermal monitoring experiment at Brady Hot Springs, Nevada both Distributed Acoustic Sensing (DAS) and nodal geophones were deployed on the surface for two weeks in March 2016. The DAS array consisted of ~8 km of fiber-optic cable deployed in zig-zag pattern in shallow trench and the conventional seismometer array was composed of shallowly buried three-component geophones (Fairfield Nodal systems). Both DAS and geophones recorded continuously for fifteen days during which two moderate-sized earthquakes with a local magnitude of Mw=4.3 (3/21/16) and Mw=4.1 (3/22/16) were recorded. Both events were recorded at similar epicentral distances (129 km and 156 km) and backazimuths (172° and 159°) with respect to Brady Hot Springs. These earthquakes provided a unique opportunity to investigate coda envelope amplitude response similarities between DAS and geophone and potential to estimate Mw using coda waves. Several DAS line segments with co-located geophone stations were used to compare the amplitude variation using narrow-band S-wave coda envelopes. Initial calculations of DAS coda envelope decay at each point showed remarkable similarity with geophone coda envelopes at all frequencies. As coda waves arrive from a range of azimuths, the azimuthal sensitivity of DAS is somewhat ameliorated. 

Presenting Author: Rengin Gok

Authors