THE DETERMINATION OF SOURCE MECHANISMS OF SMALL EARTHQUAKES BY MOMENT TENSOR INVERSION

D. Malytskyy; D. Mikesell

doi:10.17721/1728-2713.92.15

Authors

D. Malytskyy Carpathian Branch of Subbotin Institute of Geophysics, NAS of Ukraine, 3-b Naukova Str., Lviv, 79060, Ukraine
D. Mikesell Carpathian Branch of Subbotin Institute of Geophysics, NAS of Ukraine, 3-b Naukova Str., Lviv, 79060, Ukraine; The Department of Geosciences at Boise State University, 1910 University Drive, Boise, Idaho, 83725 The USA

DOI:

https://doi.org/10.17721/1728-2713.92.15

Keywords:

seismic moment tensor, source mechanism, small earthquakes, matrix method

Abstract

A method is presented for moment tensor inversion of only direct P-waveforms registered at only one station and a limited number of stations. The method is based on an inversion approach described in where a version of the matrix method has been developed for calculation of direct P-waves in horizontally layered half-space from a point source represented by its moment tensor. We describe a procedure for retrieving the source mechanism of small earthquakes based on interactive inversion of seismograms and demonstrate its application to two local earthquakes in the Boise region. The moment tensor inversion of seismogram data in this study is based on a point source model. The process includes generation of synthetic seismograms using the matrix method for an elastic, horizontallylayered, medium. In the paper, a method is presented for moment tensor inversion of only direct P- waves, which are less sensitive to path effects than reflected and converted waves. This approach significantly improves the inversion method accuracy and reliability. A pointsource approximation is considered, with known location and origin time. Based on forward modeling, a numerical technique is developed for the inversion of observed waveforms for time history of the components of moment tensor M(t), obtained by generalized inversion.

References

Aki, K., Richards, P.G. (1980). Quantitative Seismology: Theory and Methods. Vol. I. San Francisco: W.H. Freeman.

Arvidsson, R. (1996). Fennoscandian earthquakes: Whole crustal rupturing related to postglacial rebound. Science, 274, 744–746.

Arvidsson, R., Kulhanek, O. (1994). Seismodynamics of Sweden deduced from earthquake focal mechanisms, Geophys. J. Int., 116, 377–392.

Camelbeeck, T., Iranga, M.D. (1996). Deep crustal earthquakes and active faults along the Rukwa trough, eastern Africa. Geophys. J. Int., 124, 612–630.

Langston, C.A., Helmberger, D.V. (1975). A procedure for modelling shallow dislocation sources. Geophys. J. R. astr. Soc., 42, 117–130.

Dziewonski, A., Woodhouse, J. (1983). An experiment in the systematic study of global seismicity: Centroid moment tensor solutions for 201 moderate and large earthquakes of 1981. J. geophys. Res., 88, 3247–3271.

Fan, G., Wallace, T. (1991). The determination of source parameters for small earthquakes from a single, very broadband seismic station. Geophys. Res. Lett., 18, 1385–1388.

Ferdinand, R.W, Arvidsson, R. (2002). The determination of source mechanisms of small earthquakes and revised models of local crustal structure by moment tensor inversion. Geophys. J. Int., 151, 221–234.

Gilbert, F. (1970). Excitation of the normal modes of the Earth by earthquake sources. Geophys. J. R. astr. Soc., 22, 223–226.

Given, J., Wallace, T., Kanamori, H. (1982). Teleseismic analysis of the 1980 Mammoth Lakes earthquake sequence. Bull. seism. Soc. Am., 72, 1093–1109.

Godano, M., Bardainne, T., Regnier, M., Deschamps, A. (2011). Moment tensor determination by nonlinear inversion of amplitudes. Bull.seism. Soc.Am., 101, 366–378.

Hardebeck, J.L., Shearer, P.M. (2003). Using S/P amplitude ratios to constrain the focal mechanisms of small earthquakes. Bull.seism. Soc.Am., 93, 2432–2444.

Jost, M.L., Herrmann, R.B. (1989). A student's guide and review of moment tensors. Seism. Res. Lett., 60, 37–57.

Kim, W.-Y. (1987). Modelling short-period crustal phases at regional distances for the seismic source parameter inversion. Phys. Earth planet. Inter., 47, 159–177.

Koch, K. (1991, a). Moment tensor inversion of local earthquake data–I. Investigation of the method and its numerical stability with model calculations. Geophys. J. Int., 106, 305–319.

Lay, T., Wallace, T. (1995). Modern Global Seismology. International Geophysics Series 58. San Diego: Academic Press.

Mai M., Schorlemmer D., Page M. et al. (2016). The Earthquake-Source Inversion Validation (SIV) Project. Seism. Res. Lett., 87, 690–708. doi: 10.1785/0220150231.

Malytskyy, D. (2016). Mathematical modeling in the problems of seismology. Kyiv: Naukova Dumka. [in Ukrainian]

Malytskyy D. (2010). Analytic-numerical approaches to the calculation of seismic moment tensor as a function of time. Geoinformatika, 1, 79–85. [in Ukrainian]

Malytskyy, D., Kozlovskyy, E. (2014). Seismic waves in layered media, J. of Earth Science and Engineering, 4, 311–325.

Malytskyy, D., D'Amico, S. (2015). Moment tensor solutions through waveforms inversion. ISBN: 978-88-98161-13-3. Mistral Service S.a.S., Earth and Enviromental Sciences.

Mao, W.J., Panza, G.F., Sulhadolc, P. (1994). Linearized waveform inversion of local and near-regional events for source mechanism and rupturing processes. Geophys. J. Int., 116, 784–798.

Nabelek, J.L. (1984). Determination of earthquake source parameters from inversion of body waves. PhD thesis. Massachusetts Institute of Technology, Cambridge.

Nabelek, J., Xia, G. (1995). Moment-tensor analysis using regional data: application to the 25 March, 1993, Scotts Mills, Oregon, earthquake. J. geophys. Res., 22, 13–16.

Pang, G, Koper, K.D., Stickney, M.C. et al. (2018). Seismicity in the Challis, Idaho, Region, January 2014–May 2017: Late Aftershocks of the 1983 Ms 7.3 Borah Peak Earthquake. Seism. Res. Lett., 89, 1366–1378.

Saikia, C.K., Herrmann, R.B. (1985). Application of waveform modeling to determine focal mechanisms of four 1982 Miramichi aftershocks. Bull. seism. Soc. Am., 75, 1021-1040.

Shemeta, J.E. (1989). New analyses of three-component digital data for aftershocks of the 1983 Borah Peak, Idaho, earthquake: Source parameters and refined hypocenters. M.S. Thesis. Department of Geology and Geophysics, University of Utah.

Shomali, Z.H., Slunga, R. (2000). Body wave moment tensor inversion of local earthquakes: an application to the South Iceland seismic zone. Geophys. J. Int., 140, 63–70.

Sileny, J., Psencik, I. (1995). Mechanisms of local earthquakes in 3D inhomogeneous media determined by waveform inversion. Geophys. J. Int., 121, 459–474.

Sileny, J., Panza, G.F., Campus, P. (1992). Waveform inversion for point source moment tensor retrieval with variable hypocentral depth and structural model. Geophys. J. Int., 109, 259-274.

Sileny, J., Campus, P., Panza, G.F. (1996). Seismic moment tensor resolution by waveform inversion of a few local noisy records–I. Synthetic tests. Geophys. J. Int., 126, 605–619.

Singh, S.K., Ordaz, M., Pacheco, J.F., Courboulex, F. (2000). A simple source inversion scheme for displacement seismograms recorded at short distances. J. Seism., 4, 267–284.

Sipkin, S.A. (1986). Estimation of earthquake source parameters by the inversion of waveform data, global seismicity 1981–1983. Bull. seism. Soc. Am., 76, 1515–1541.

Stump, B.W., Johnson, L.R. (1977). The determination of source properties by the linear inversion of seismograms. Bull. seism. Soc. Am., 67, 1489–1501.

Vavrychuk V., Kuhn D. (2012). Moment tensor inversion of waveforms: a two-step time frequency approach. Geophys. J. Int., 190, 1761–1776.

Weber, Z. (2016). Probabilistic waveform inversion for 22 earthquake moment tensors in Hungary: new constraints on the tectonic stress pattern inside the Pannonian basin. Geophys. J. Int., 204, 236–249.

Weber, Z. (2006). Probabilistic local waveform inversion for moment tensor and hypocentral location. Geophys. J. Int., 165, 607–621.

Zhao, L-S., Helmberger, D.V. (1994). Source estimation from broadband regional seismograms. Bull. seism. Soc. Am., 84, 91–104.

Zhu, L., Helmberger, D.V. (1996). Advancement in source estimation techniques using broadband regional seismograms. Bull. seism. Soc. Am., 86, 1634–1641.