Using seismic waveform data, we determine seismic moment tensor solutions for six events in the Minto Flats fault zone, 2012-2016.This project was supported by the National Science Foundation, Grant EAR-1352688

Silwal, Vipul

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Text Supplement for SholarWorks@UA olletionSeismi moment tensors for six events in the Minto Flats fault zone, 20122016Vipul SilwalVersion 1: April 4, 2018Attribution: If you use these les, please ite Tape et al. (2018) and Silwal (2018).Desription of lesThis olletion is established as a supplement to a published manusript (Tape et al., 2018).Seismi moment tensors were estimated using body waves and surfae waves. The best solution(M0) was obtained through a grid-searh in the moment tensor spae using the `ut-and-paste'(CAP) approah, whih allows for dierent frequenies and time shifts on dierent portions ofseismograms (Zhao and Helmberger , 1994; Zhu and Helmberger , 1996; Zhu and Ben-Zion, 2013).The moment tensor approah was adapted and applied in Silwal and Tape (2016) and Silwal et al.(2018) for double ouple moment tensors and in Alvizuri and Tape (2016) for full moment tensors.A summary of les in the olletion is listed in the following table:le name desriptionsholarworks.pdf this le: summary of olletionwaveform_ts_ALL.pdf Figure A: waveform tsbeahballs_ALL.pdf Figure B: beahball plots with piering pointsdepth_tests_ALL.pdf Figure C: depth grid searh plotsnennu_meh.txt text le atalog of moment tensorsnennu_weights.zip zipped set of text les of input parameters for moment tensorinversionsnennu_mt.pdf moment tensor inversions with varying soure durationWithin eah set of gures (A, B, C), the 6 events are in hronologial order by origin time.Figure A: Waveform tsWaveform ts for 6 moment tensor inversions. An example is inluded here as Figure A3. Blakare observed waveforms; red are syntheti waveforms omputed using a frequeny-wavenumbermethod (Zhu and Rivera, 2002) that assumes a (1D) layered model. The waveforms are tseparately within ve time windows: P wave vertial omponent (PV), P wave radial omponent(PR), Rayleigh wave vertial omponent (SurfV), Rayleigh wave horizontal omponent (SurfR),and Love wave transverse omponent (SurfT). At far left in eah row is the station name, soure-station distane in km, and station azimuth in degrees. Below eah pair of waveforms are fournumbers: the ross-orrelation time shift between data and synthetis, the ross-orrelation value,the perent of the mist funtion represented by the waveform pair, and the amplitude ratiobetween waveforms, ln(Aobs/Asyn), where A is the max value of the waveform within the timewindow.The beahball represents the best solutionM0 (i.e., the global minimum of the mist funtion).The beahball is plotted as a lower-hemisphere projetion (standard seismologial onvention) ofthe moment tensor. The surrounding blak dots denote the azimuthal loation of the stationsused, and the red rosses denote the lower hemisphere piering points of the ray paths to thestations.Here is a header for an example event in Figure A3: The four header lines are as follows:11. Event 20150912032512711 Model tatmod Depth 21The event ID is derived from the origin time of 2015-09-12 03:25:12.711.The layered model used is tatmod, and the event depth is 21 km.2. FM 211 50 -16 Mw 3.80 γ 0 δ 0 rms 2.253e-01 VR 94.9 pol_wt 999.00The orientation of the moment tensor solutionM0 is strike 211◦, dip 50◦, rake −16◦. The es-timated magnitude isMw 3.8. The soure type ofM0 is expressed in terms of lune longitudeγ = 0◦ and lune latitude δ = 0◦. Sine we are searhing only in double ouple spae, γ andδ are zero for all solutions (see (Alvizuri et al., 2018)). The waveform dierene betweendata and synthetis is RMS = 2.253e − 01, and the variane redution is VR = 94.9%.These are based on a waveform dierene measure that rewards using longer time windowsand broader bandpass limits. This hoie means that the VR annot be diretly omparedwith VR values reported in other studies. If polarities are use in the mist funtion, thenthe fator pol_wt determines the balane between tting waveforms and tting polarities.A value of 999.0 means that polarities are not used.3. Filter periods (seonds): Body:0.50-2.50. Surf:20.00-50.00 duration: 12.00/6.00 sThe body waves were ltered 0.502.50 s, the surfae waves were ltered 20.0050.00 s. Thesoure time funtion is a trapezoidal funtion whose duration is 12.00 s and whose rise timeis half the duration. The duration is not an estimated soure parameter but is set suh thatit gives the highest VR(see nennu_mt.pdf for detailed analysis).4. # norm L1 # Pwin 6 Swin 200 # N 13 Np 0 Ns 38An L1 norm was used for the mist funtion (e.g., Silwal and Tape, 2016). The (referene)P-window is 6 s long and the surfae wave window is 200 s long. Again, these parametersare meaningful only if the body or surfae wave omponents are used for inversion. From atotal of 13 stations (N), 0 P wave windows (Np), and 38 surfae wave windows (Ns) wereused. In this example, body waves are not used.The numbers below eah station are1. sourestation epientral distane, km2. station azimuth, in degrees3. time shift between piked P onset and syntheti P onset.4. sign of the observed rst-motion polarity, whih is either 1 (up or ompression) or −1 (downor dilatation). The number in parentheses is the predited amplitude, whih ranges between±√2; numbers lose to zero indiate that the station is near a nodal surfae of the radiationpattern for the assumed mehanism.The four numbers below eah pair of waveforms are1. the ross-orrelation time shift ∆T = Tobs − Tsyn required for mathing the synthetis s(t)with the data u(t). A positive time-shift means that the synthetis arrive earlier than thedata and that the assumed veloity model is faster than the atual earth struture.2. the maximum ross-orrelation perentage between u(t) and s(t−∆T )3. the perentage of the total mist4. the amplitude ratio ln(Aobs/Asyn) in eah time window2Figure B: Beahballs with piering pointsAn example gure is shown in Figure B3.The two header lines are as follows:1. Event 20150912032512711 Model 20150912032512711_tatmod_021Same as the header line 1 for waveform ts plot.2. FM 211 50 -16 Mw 3.80 γ 0 δ 0 rms 2.253e-01 VR 94.9 pol_wt 999.00Same as the header line 2 for waveform ts plot.The dot (·) at the station name outside marks the soure-station azimuth. The lowerhemisphere piering points are marked with a ross (x). The upper hemisphere pieringpoints are marked with a irle (o).Figure C: Depth grid searh plotAn example depth grid searh plot is shown in Figure C3.The plot shows the best-tting depth grid searh for 6 events. The depth inrement for thegrid searh is 1 km. The red inverted triangle marks the Alaska Earthquake Center atalog depth,and the white inverted triangle marks the depth obtained from the moment tensor inversion. Theblue tik marks on the x-axis mark the layer boundaries in the 1D model (tatmod) used in themoment tensor inversions. The plot shows the variane redution (gray urve) with sale on theright. On the left is the variane redution relative to the minimum variane redution. Thedepth unertainty is alulated based on the depth at whih the variane redution is 0.10 worsethan at the best solution. Note that the earthquake magnitude is free to hange for eah depth,and it generally inreases with inreasing depth for the best-tting solution (at a given depth), aswe might expet.Text le tables for moment tensor atalogs [nennu_meh.txt℄Seismi moment tensor atalog for the 6 events. Details an be found within the header lines,whih also refer to Kanamori (1977); Aki and Rihards (1980); Silver and Jordan (1982); Minsonet al. (2007); Tape and Tape (2012, 2013, 2015).Input text les used in the moment tensor inversion [nennu_weights.zip℄We provide a text le for eah of the 6 events in this study. These les show whih stationsand whih time windows were used (or not) in eah moment tensor inversion. It also shows therst-motion polarity observations that were used.ReferenesAki, K., and P. G. Rihards (1980), Quantitative Seismology, Theory and Methods, W. H. Freeman,San Franiso, Calif., USA.Alvizuri, C., and C. Tape (2016), Full moment tensors for small events (Mw < 3) at Uturunuvolano, Bolivia, Geophys. J. Int., 206, 17611783, doi:10.1093/gji/ggw247.Alvizuri, C., V. Silwal, L. Krisher, and C. Tape (2018), Estimation of full moment tensors, in-luding unertainties, for nulear explosions, volani events, and earthquakes, J. Geophys. Res.Solid Earth (in revision).Kanamori, H. (1977), The energy release in great earthquakes, J. Geophys. Res., 82, 29812987.3Minson, S. E., D. S. Dreger, R. Bürgmann, H. Kanamori, and K. M. Larson (2007), Seismiallyand geodetially determined nondouble-ouple soure mehanisms from the 2000 Miyakejimavolani earthquake swarm, J. Geophys. Res., 112, B10308, doi:10.1029/2006JB004847.Silver, P. G., and T. H. Jordan (1982), Optimal estimation of salar seismi moment, Geophys. J.R. Astron. So., 70, 755787.Silwal, V. (2018), Seismi moment tensors for six events in the Minto Flats fault zone, 20122016,SholarWorksUA: desriptor le, text le of atalog, gures with waveform ts, and inputweight les.Silwal, V., and C. Tape (2016), Seismi moment tensors and estimated unertainties in southernAlaska, J. Geophys. Res. Solid Earth, 121, 27722797, doi:10.1002/2015JB012588.Silwal, V., C. Tape, and A. Lomax (2018), Crustal earthquakes in the Cook Inlet and Susitnaregion of southern Alaska, Tetonophysis(in review).Tape, C., et al. (2018), Earthquake nuleation and fault slip omplexity in the lower rust ofentral Alaska, Nature Geosiene (in review).Tape, W., and C. Tape (2012), A geometri setting for moment tensors, Geophys. J. Int., 190,476498, doi:10.1111/j.1365-246X.2012.05491.x.Tape, W., and C. Tape (2013), The lassial model for moment tensors, Geophys. J. Int., 195,17011720, doi:10.1093/gji/ggt302.Tape, W., and C. Tape (2015), A uniform parameterization of moment tensors, Geophys. J. Int.,202, 20742081, doi:10.1093/gji/ggv262.Zhao, L.-S., and D. V. Helmberger (1994), Soure estimation from broadband regional seismo-grams, Bull. Seismol. So. Am., 84 (1), 91104.Zhu, L., and Y. Ben-Zion (2013), Parameterization of general seismi poteny and moment tensorsfor soure inversion of seismi waveform data, Geophys. J. Int., 194, 839843, doi:10.1093/gji/ggt137.Zhu, L., and D. Helmberger (1996), Advanement in soure estimation tehniques using broadbandregional seismograms, Bull. Seismol. So. Am., 86 (5), 16341641.Zhu, L., and L. A. Rivera (2002), A note on the dynami and stati displaements from a pointsoure in multilayered media, Geophys. J. Int., 148, 619627, doi:10.1046/j.1365-246X.2002.01610.x.46 secs. 80 secs.AK.MDM..BH27 km131° TA.I23K..BH32 km275° TA.TCOL..BH46 km125° XV.FTGH..HH48 km189° XV.F6TP..HH50 km236° TA.POKR..BH57 km89° AK.NEA2..BH61 km198° XV.F8KN..HH71 km237° TA.H24K..BH87 km24° TA.H23K..BH88 km332° AK.MLY..BH98 km265° AK.HDA..BH113 km133° TA.J25K..BH166 km108° P V P R9.90830.86−0.309.90801.05−0.0412.24981.120.24Surf V Surf R Surf T11.22963.68−0.2511.22994.19−0.0711.14981.800.0610.54920.81−0.0310.54951.41−0.1111.72981.290.0111.66971.94−0.0411.66495.460.0912.82922.94−0.0511.30953.46−0.4011.30984.60−0.0211.60942.700.1211.88952.910.1311.88972.77−0.2712.18861.410.0212.22981.630.0112.22952.25−0.0111.22762.65−0.0011.22984.17−0.0610.92934.610.2112.28963.590.3612.28974.050.0811.52944.820.1312.46911.730.2112.46983.070.1511.50962.490.1011.48871.960.5311.48973.370.0111.42882.110.0411.72951.210.2911.72692.190.2911.00982.36−0.0311.92852.500.4211.92732.650.1011.40982.20−0.01Event 20150912032512711 Model tactmod Depth 21FM 211 50 −16 Mw 3.80 γ   0 δ   0 rms 2.253e−01 VR 94.9 pol_wt 999.00 Filter periods (seconds): Body:0.50−2.50. Surf:20.00−50.00 duration: 12.00/6.00 s# norm L1    # Pwin 6 Swin 200    # N 13 Np 0 Ns 38Figure A3: Example from p. 3 of the set of 6 pages in Figure A.5AK.MDM.TA.I23K.TA.TCOL.XV.FTGH.XV.F6TP.TA.POKR.AK.NEA2.8KNTA.H24K.TA.H23K.AK.MLY.AK.HDA.TA.J25K.AK.MDM.TA.I23K.TA.TCOL.XV.FTGH.XV.F6TP.TA.POKR.AK.NEA2.XV.F8KN.TA.H24K.TA.H23K.AK.MLY.AK.HDA.TA.J25K.Event 20150912032512711 Model 20150912032512711_tactmod_021FM 211 50 −16 Mw 3.80 γ   0 δ   0 rms 2.253e−01 VR 94.9 pol_wt 999.00Figure B3: Example from p. 3 of the set of 6 pages in Figure B.60.0000.0060.0120.0180.0240.030ln(VR_max / VR)ln(VR_max / VR)020406080100VR (gray)10 15 20 25 30Depth, kmVR (gray)VR (gray)VR (gray)VR (gray)VR (gray)VR (gray)VR (gray)VR (gray)3.803.803.803.803.803.803.803.803.803.80 3.803.803.803.803.803.803.8020150912032512711 | Model tactmod | Best depth 21.2 ± 4.2 kmFigure C3: Example from p. 3 of the set of 6 pages in Figure C.7

Seismic moment tensors for six events in the Minto Flats fault zone, 2012-2016

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Seismic moment tensors for six events in the Minto Flats fault zone, 2012-2016

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