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Title: Moment-tensor joint inversion of microseismic events using finite-difference waveform simulation

Authors:
 [1]; ORCiD logo [1]
  1. Los Alamos National Laboratory
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1352358
Report Number(s):
LA-UR-17-22822
DOE Contract Number:
AC52-06NA25396
Resource Type:
Conference
Resource Relation:
Conference: Carbon Capture, Utilization and Storage 2017 ; 2017-04-10 - 2017-04-13 ; Chicago, Illinois, United States
Country of Publication:
United States
Language:
English
Subject:
Earth Sciences

Citation Formats

Chen, Yu, and Huang, Lianjie. Moment-tensor joint inversion of microseismic events using finite-difference waveform simulation. United States: N. p., 2017. Web.
Chen, Yu, & Huang, Lianjie. Moment-tensor joint inversion of microseismic events using finite-difference waveform simulation. United States.
Chen, Yu, and Huang, Lianjie. Wed . "Moment-tensor joint inversion of microseismic events using finite-difference waveform simulation". United States. doi:. https://www.osti.gov/servlets/purl/1352358.
@article{osti_1352358,
title = {Moment-tensor joint inversion of microseismic events using finite-difference waveform simulation},
author = {Chen, Yu and Huang, Lianjie},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Apr 19 00:00:00 EDT 2017},
month = {Wed Apr 19 00:00:00 EDT 2017}
}

Conference:
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  • Using a regional time-domain waveform inversion for the complete moment tensor we calculate the deviatoric and isotropic source components for several explosions at the Nevada Test Site as well as earthquakes, and collapses in the surrounding region of the western US. The events separate into specific populations according to their deviation from a pure double-couple and ratio of isotropic to deviatoric energy. The separation allows for anomalous event identification and discrimination between explosions, earthquakes, and collapses. Error in the moment tensor solutions and source parameters is also calculated. We investigate the sensitivity of the moment tensor solutions to Green's functionsmore » calculated with imperfect Earth models, inaccurate event locations, and data with a low signal-to-noise ratio. We also test the performance of the method under a range of recording conditions from excellent azimuthal coverage to cases of sparse station availability, as might be expected for smaller events. Finally, we assess the depth and frequency dependence upon event size. This analysis will be used to determine the range where well-constrained solutions can be obtained.« less
  • The deviatoric and isotropic source components for 17 explosions at the Nevada Test Site, as well as 12 earthquakes and 3 collapses in the surrounding region of the western US, are calculated using a regional time-domain full waveform inversion for the complete moment tensor. The events separate into specific populations according to their deviation from a pure double-couple and ratio of isotropic to deviatoric energy. The separation allows for anomalous event identification and discrimination between explosions, earthquakes, and collapses. Confidence regions of the model parameters are estimated from the data misfit by assuming normally distributed parameter values. We investigate themore » sensitivity of the resolved parameters of an explosion to imperfect Earth models, inaccurate event depths, and data with a low signal-to-noise ratio (SNR) assuming a reasonable azimuthal distribution of stations. In the band of interest (0.02-0.10 Hz) the source-type calculated from complete moment tensor inversion is insensitive to velocity models perturbations that cause less than a half-cycle shift (<5 sec) in arrival time error if shifting of the waveforms is allowed. The explosion source-type is insensitive to an incorrect depth assumption (for a true depth of 1 km), but the goodness-of-fit of the inversion result cannot be used to resolve the true depth of the explosion. Noise degrades the explosive character of the result, and a good fit and accurate result are obtained when the signal-to-noise ratio (SNR) is greater than 5. We assess the depth and frequency dependence upon the resolved explosive moment. As the depth decreases from 1 km to 200 m, the isotropic moment is no longer accurately resolved and is in error between 50-200%. However, even at the most shallow depth the resultant moment tensor is dominated by the explosive component when the data has a good SNR. The sensitivity investigation is extended via the introduction of the network sensitivity solution, which takes into account the unique station distribution, frequency band, and SNR of a given test scenario. An example of this analysis is presented for the North Korea test, which shows that in order to constrain the explosive component one needs a certain station configuration. In the future we will analyze the bias in the source-type parameters due to error in the Green's function by incorporating a suite of suitable velocity models in the inversion.« less
  • In our previous work the deviatoric and isotropic source components for 17 explosions at the Nevada Test Site, as well as 12 earthquakes and 4 collapses in the surrounding region of the western US, were calculated using a regional time-domain full waveform inversion for the complete moment tensor (Dreger et al., 2008; Ford et al., 2008; Ford et al., 2009a). The events separate into specific populations according to their deviation from a pure double-couple and ratio of isotropic to deviatoric energy. The separation allows for anomalous event identification and discrimination between explosions, earthquakes, and collapses. Confidence regions of the modelmore » parameters are estimated from the data misfit by assuming normally distributed parameter values. We developed a new Network Sensitivity Solution (NSS) in which the fit of sources distributed over a source-type plot (Hudson et al., 1989) show the resolution of the source parameters. The NSS takes into account the unique station distribution, frequency band, and signal-to-noise ratio of a given event scenario. The NSS compares both a hypothetical pure source (for example an explosion or an earthquake) and the actual data with several thousand sets of synthetic data from a uniform distribution of all possible sources. The comparison with a hypothetical pure source provides the theoretically best-constrained source-type region for a given set of stations, and with it one can determine whether further analysis with the data is warranted. We apply the NSS to a NTS nuclear explosion, and earthquake, as well as the 2006 North Korean explosion, and a nearby earthquake. The results show that explosions and earthquakes are distinguishable, however the solution space depends strongly on the station coverage. Finally, on May 25, 2009 a second North Korean test took place. Our preliminary results show that the explosive nature of the event may be determined using the regional distance moment tensor method. Results indicate that the 2009 event is approximately 5-6 times larger than the earlier test, with an isotropic moment of about 1.8e+22 dyne cm. We perform a series of inversions for pure double-couple, pure explosion, combined double-couple and explosion, full moment tensor, and damped moment tensor inversions to assess the resolution of the isotropic moment of the event.« less