Determining source parameters from waveforms of small earthquakes in the Carpathian region of Ukraine
DOI:
https://doi.org/10.24028/gzh.0203-3100.v40i6.2018.151041Keywords:
small earthquakes, seismic moment tensor, focal mechanism, matrix methodAbstract
In the paper, a method is presented for moment tensor inversion of only direct P- and/or S-waves registered at only one station. Lesser sensitivity of direct waves, if compared to reflected and converted waves, to path effects modeling significantly improves the method’s accuracy and reliability. Choosing to invert only the direct P-waves, calculated by matrix method, instead of the full field, enables to reduce the effects of the half-space model inaccuracy, reflected and converted phases being much more distorted by it. Point-source approximation is considered, with known location and origin time. Wave propagation in the medium modelled as horizontally layered heterogeneous elastic structure is calculated by matrix method, enabling to isolate only direct waves. Based on forward modeling, a numerical technique is developed for the inversion of observed waveforms for the components of moment tensor M(t), obtained by generalized inversion. The proposed inversion method is applied to three small earthquakes from the East Carpathian region to retrieve their moment tensors from waveforms registered at only one station. The resulting focal mechanisms are compared between the stations and with determined from polarities of first arrivals. It should also be pointed out that all three mechanisms determined here by the inversion of waveforms indicate northward thrusting, which occurs in a good agreement with predominantly NNE orientation (~60°) of principal compression stresses within the region revealed by different methods as well as with main features of local tectonics. The mechanisms also are compared with focal mechanisms estimated from first P-wave polarities. A conclusion is drawn out that the method will be useful when focal mechanisms can’t be obtained by other methods, the problem typical for the regions with low seismicity and insufficient number of seismic stations.
References
Malytskyy, D. V. (2010). Analytic-numerical approaches to the calculation of seismic moment tensor as a function of time. Geoinformatyka, (1), 79—85 (in Ukrainian).
Malytskyy, D. V. (2016). Mathematical modeling in problems of seismology. Kiev: Naukova Dumka (in Ukrainian).
Malitskiy, D. V., Murovskaya, A. V., Obidina, A. A., Gintov, O. B., Gnip, A. G., & Pugach, A. V. (2017). Stress field in the Transcarpathians from focal mechanisms. 16th International Conference on Geoinformatics — Theoretical and Applied Aspects, May 15—17, 2017, Kiev, Ukraine. doi: 10.3997 / 2214-4609.201701862 (in Russian).
Khomenko, V. I. (1971). The deep structure of the Transcarpathian trough. Kyiv: Naukova Dumka (in Ukrainian).
Khomenko, V. I. (1987). Depth structure of the southwestern edge of the East European Platform. Kiev: Naukova Dumka (in Russian).
Aki, K. & Richards, P. G. (2002). Quantitative seismology — Theory and methods. Sausalito, California: University Science Books.
Arvidsson, R. & Ekström, G. (1998). Global CMT analysis of moderate earthquakes, Mw≥4.5, using intermediate-period surface waves. Bulletin of the Seismological Society of America, 88(4), 1003—1013.
D’Amico, S. (2014). Source parameters related to a small earthquake swarm off-shore of Malta (central Mediterranean). Development in Earth Science, (2), 8—13.
Dreger, D. S. & Helmberger, D. V. (1993). Determination of source parameters at regional distances with three-component sparse network data. Journal of Geophysical Research, 98(B5), 8107—8125. https://doi.org/10.1029/93JB00023.
Dreger, D. S. (2003). TDMT_INV: Time domain
seismic moment tensor inversion. In W.H.K. Lee,
H. Kanamori, P. C. Jennings & C. Kisslinger (Eds), International Geophysics (Vol. 81). Academic Press.
Dziewonski, A. M, Chou, T. A., & Woodhouse, J. H. (1981). Determination of earthquake source parameters from waveform data for studies of regional and global seismicity. Journal of Geophysical Research, 86(B4), 2825—2852. https://doi.org/10.1029/JB086iB04p02825.
Godano, M., Bardainne, T., Regnier, M., & Deschamps, A., (2011). Moment tensor determination by nonlinear inversion of amplitudes. Bulletin of the Seismological Society of America, 101(1), 366—378. https://doi.org/10.1785/ 0120090380.
Hardebeck, J. L., & Shearer, P. M. (2003). Using S/P amplitude ratios to constrain the focal mechanisms of small earthquakes. Bulletin of the Seismological Society of America, 93(6), 2434—2444. https://doi.org/10.1785/0120020236.
Herrmann, R. B. (2002). An overview of synthetic seismogram computation, computer programs in Seismology. Saint Louis University.
Herrmann, R. B. (2008). Toward automated focal mechanism and moment determination for the continental U.S. — an ANSS product. Final Technical Report USGS Grant 05HQGR0047.
Herrmann, R. B., Withers, M. & Benz, H. (2008). The April 18, 2008 Illinois earthquake: an ANSS monitoring success. Seismological Research Letters, 79(6), 830—843. https://doi.org/10.1785/gssrl.79.6.830
Mai, M., Schorlemmer, D., Page, M., Ampuero, J.-P., Asano, K., Causse, M., … Zielke, O. (2016). The Earthquake-Source Inversion Validation (SIV) Project. Seismological Research Letters, 87(3), 690—708. doi: 10.1785/0220150231.
Malytskyy, D. & D’Amico, S. D. (2015). Moment tensor solutions through waveforms inversion. Published by Mistral Service sas Via U. Bonino, Messina, Italy.
Malytskyy, D., & Kozlovskyy, E., (2014). Seismic waves in layered media. Journal of Earth Science and Engineering, (4), 311—325.
Malytskyy,D., Muyla, O., Pavlova, A., & Hrytsay, O. (2013). Determination the focal mechanism of an earthquake in the Transcarpathia region of Ukraine. Visnyk Kyyivskoho natsionalnoho universytetu imeni Tarasa Shevchenka. Heolohiya, (4), 38—44.
Miller, A. D., Julian, B. R., & Foulger, G. R. (1998). Three-dimensional seismic structure and moment tensors of non-double-couple earthquakes at the Hengill-Grensdalur volcanic complex, Iceland. Geophysical Journal International, 133(2), 309—325. https://doi.org/10.1046/j.1365-246X.1998.00492.x.
Šílený, J., Panza, G. F., & Campus, P. (1992). Waveform inversion for point source moment tensor retrieval with variable hypocentral depth and structural model. Geophysical Journal International, 109(2), 259—274. https://doi.org/10.1111/j.1365-246X.1992.tb00097.x.
Sipkin, S. A. (1986). Estimation of earthquake source parameters by the inversion of waveform data: Global seismicity, 1981—1983. Bulletin of the Seismological Society of America, 76, 1515—1541.
Vavryčuk, V., & Kühn, D. (2012). Moment tensor inversion of waveforms: a two-step time frequency approach. Geophysical Journal International, 190 (3), 1761—1776. https://doi.org/10.1111/j.1365-246X.2012.05592.x
Wéber, Z. (2006). Probabilistic local waveform inversion for moment tensor and hypocentral location, Geophysical Journal International, 165(2), 607—621. https://doi.org/10.1111/j.1365-246X.2006.02934.x
Wéber, Z. (2016). Probabilistic waveform inversion for 22 earthquake moment tensors in Hungary: new constraints on the tectonic stress pattern inside the Pannonian basin. Geophysical Journal International, 204(1), 236—249. https://doi.org/10.1093/gji/ggv446.
Zhu, L., Akyol, N., Mitchell, B., & Sozbilir, H. (2006). Seismotectonics of western Turkey from high resolution earthquake relocations and moment tensor determinations. Geophysical Research Letters, 33(7), L07316. doi: 10.1029/ 2006GL025842.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2020 Geofizicheskiy Zhurnal
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this journal agree to the following terms:
1. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
2. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
3. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).