Source Characterization Of Microearthquakes Induced By Hydraulic Fracturing With Empirical Green's Function
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1995.7 Li_Cheng_Toksoz.pdf
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Author(s)
Li, Yingping
Cheng, C. H.
Toksoz, M. Nafi
Date Issued
1995
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1995-07
Abstract
In this paper, we retrieved relative source time functions (RSTF) and estimated the
source parameters for microearthquakes (M= -1.9 to -2.6) induced by hydraulic injection
at Fenton Hill, New Mexico, using an empirical Green's function (EGF) method.
Seismic waveform of a small event in seismic doublets or multiplets (Gelle and Meuller,
1980), defined as co-located events with similar focal mechanisms, within a hydraulic
fracture zone, is treated as the EGF and is deconvolved from that of a larger event in the doublets or multiplets to retrieve the relative source time function. Time domain analysis of the RSTFs reveals the source complexity of the induced microearthquakes. The
azimuthal variation of the RSTF indicates that the rupture propagates to the northwest,
which is consistent with the growth direction of the hydraulic fracture zone determined
by Li and Cheng (1995) with a seismicity temporal-spatial distribution pattern. The
source duration of the induced events ranges from 2 to 8 ms and the source radii are
estimated to be 4 to 12 meters. Values of stress drops are from 1 to 19 bars. Significant
variation of the stress drops may reflect the heterogeneity of the stress field in the
hydraulic fracture zone and its vicinity and indicate that the stress field heterogeneity
extends down to a few meters.
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