Input for Bayesloc calculations for locating the 27 February 2022 Lop Nor earthquake

Steven J Gibbons, NGI<br> 2022-04-04 The directories contained within this tar file contain all the files needed to calculate the location estimates<br> of the 2022-02-27 Lop Nor earthquake using the Bayesloc program with various sets of<br> inputs.<br> No output is included, only the input files: bayesloc.cfg<br> arrival.dat<br> station.dat<br> origin_prior.dat<br> and any traveltime tables needed. In each directory, the Bayesloc program is run by typing bayesloc bayesloc.cfg The directories are as follows: (a) USGS_P1only_singleevent<br> The following 5 files needed to locate using only the first P arrivals<br> in the NEIC solution (see Data and resources) ak135_P1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat (b) superset_singleevent<br> The following 6 files needed to locate using a set of arrivals based upon<br> the USGS arrivals, selected arrivals from the file ISC_info_20220402.txt,<br> and manual picks made from open stations available from IRIS. ak135_P1.dat ak135_S1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat (c) 11 different directories<br> fisk_900526<br> fisk_900816<br> fisk_920521<br> fisk_920925<br> fisk_931005<br> fisk_940610<br> fisk_941007<br> fisk_950515<br> fisk_950817<br> fisk_960608<br> fisk_960729<br> <br> In each of these directories, there are the files<br> ak135_P1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat<br> needed to locate one of the 11 nuclear explosions described in Fisk (2002)<br> on an event by event basis. (d) all_events_joint_USGSonly_fixedGT This solves for the location of the 20220227 event simultaneously with the<br> locations of the 11 GT nuclear tests, using only those arrivals chosen from<br> the USGS solution for the 20220227 event<br> (i.e. the arrivals in the directory USGS_P1only_singleevent ) This directory contains five files<br> ak135_P1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat (e) all_events_joint_superset_fixedGT This solves for the location of the 20220227 event simultaneously with the<br> locations of the 11 GT nuclear tests, using the arrivals from the 20220227<br> event "superset" (i.e. the arrivals in the directory superset_singleevent ) This directory contains six files<br> ak135_P1.dat ak135_S1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat The image "locations_panel.png" contains the output from each of the Bayesloc<br> calculations in these directories, plus a few others using the same input files but with<br> changes to the origin_prior.dat files such that the GT events are not fixed to the locations<br> specified by Fisk (2002). Panel (a) displays the bulletin location estimates listed in the file<br> "ISC_info_20220402.txt" together with the GT locations of the nuclear tests provided by<br> Fisk (2002). Panel (b) displays the results from the single event location runs: i.e. the outputs<br> from all of the directories fisk_900526<br> fisk_900816<br> fisk_920521<br> fisk_920925<br> fisk_931005<br> fisk_940610<br> fisk_941007<br> fisk_950515<br> fisk_950817<br> fisk_960608<br> fisk_960729<br> superset_singleevent<br> USGS_P1only_singleevent Panel (c) displays the locations when the files in the directory<br> all_events_joint_superset_fixedGT are run but with modifications<br> to the origin_prior.dat file to remove the 1 km lateral constraint on the GT<br> events. In addition, the brown points on this map are the output from<br> the directory all_events_joint_USGSonly_fixedGT but with the origin_prior.dat<br> modified to remove the constraints of the GT events. Panel (d) displays the locations when the files in the directory<br> all_events_joint_superset_fixedGT are run as they are.<br> In addition, the brown points on this map are the output from<br> the directory all_events_joint_USGSonly_fixedGT. In panels (c) and (d) the nuclear explosion locations are only displayed<br> for the calculations in the all_events_joint_superset_fixedGT directory.<br> The locations for these events obtained in the all_events_joint_USGSonly_fixedGT<br> directory are very similar. Data and resources<br> ------------------ The Bayesloc probabilistic multiple seismic event location software was obtained from<br> https://www-gs.llnl.gov/nuclear-threat-reduction/nuclear-explosion-monitoring/bayesloc<br> (last accessed April 2022). The file ISC_info_20220402.txt is the output from a search of<br> http://www.isc.ac.uk/iscbulletin/<br> performed on April 2, 2022. (ISC, 2022) The National Earthquake Information Center earthquake report for the 27 February 2022 event is found on<br> https://earthquake.usgs.gov/earthquakes/eventpage/us6000h0k8/executive<br> (last accessed April 2022). References<br> ---------- Fisk, M. D. (2002). Accurate Locations of Nuclear Explosions at the Lop Nor Test Site Using Alignment of Seismograms and IKONOS Satellite Imagery. Bull. Seismol. Soc. Am. 92, 29112925. doi:10.1785/0120010268. International Seismological Centre (2022), On-line Bulletin, https://doi.org/10.31905/D808B830