Input for Bayesloc calculations for locating the 27 February 2022 Lop Nor earthquake
<p>Steven J Gibbons, NGI<br>
2022-04-04</p>
<p>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:</p>
<p>bayesloc.cfg<br>
arrival.dat<br>
station.dat<br>
origin_prior.dat<br>
and any traveltime tables needed.</p>
<p>In each directory, the Bayesloc program is run by typing</p>
<p>bayesloc bayesloc.cfg</p>
<p>The directories are as follows:</p>
<p>(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)</p>
<p> ak135_P1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat</p>
<p>(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.</p>
<p> ak135_P1.dat ak135_S1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat</p>
<p>(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.</p>
<p>(d) all_events_joint_USGSonly_fixedGT</p>
<p> 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 )</p>
<p> This directory contains five files<br>
ak135_P1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat</p>
<p>(e) all_events_joint_superset_fixedGT</p>
<p> 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 )</p>
<p> This directory contains six files<br>
ak135_P1.dat ak135_S1.dat arrival.dat bayesloc.cfg origin_prior.dat station.dat</p>
<p>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).</p>
<p>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).</p>
<p>Panel (b) displays the results from the single event location runs: i.e. the outputs<br>
from all of the directories</p>
<p>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</p>
<p>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.</p>
<p>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.</p>
<p>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.</p>
<p>Data and resources<br>
------------------</p>
<p>The Bayesloc probabilistic multiple seismic event location software was obtained from<br>
<a href="https://www-gs.llnl.gov/nuclear-threat-reduction/nuclear-explosion-monitoring/bayesloc">https://www-gs.llnl.gov/nuclear-threat-reduction/nuclear-explosion-monitoring/bayesloc</a><br>
(last accessed April 2022).</p>
<p>The file ISC_info_20220402.txt is the output from a search of<br>
<a href="http://www.isc.ac.uk/iscbulletin/">http://www.isc.ac.uk/iscbulletin/</a><br>
performed on April 2, 2022. (ISC, 2022)</p>
<p>The National Earthquake Information Center earthquake report for the 27 February 2022 event is found on<br>
<a href="https://earthquake.usgs.gov/earthquakes/eventpage/us6000h0k8/executive">https://earthquake.usgs.gov/earthquakes/eventpage/us6000h0k8/executive</a><br>
(last accessed April 2022).</p>
<p>References<br>
----------</p>
<p>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:<a href="http://dx.doi.org/10.1785/0120010268">10.1785/0120010268</a>.</p>
<p>International Seismological Centre (2022), On-line Bulletin, <a href="https://doi.org/10.31905/D808B830">https://doi.org/10.31905/D808B830</a></p>
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