Abstract
Selected problems related to accurate hypocenter locations are discussed in the difficult case that only reliable P-wave readings are available. Near stations are usually only few, and often have a poor azimuthal coverage. As such, they are insufficient because the inversion is highly ill-posed, and the epicenter position strongly trades-off with depth. Thus more distant stations are also needed to obtain the correct epicenter. However, joint use of near and distant stations present another difficulty; it may yield a significantly incorrect depth estimate in case that the crustal model is not fully appropriate. In practice, the erroneous depth often remains unrecognized. An indication of the depth problem can be obtained by analyzing the travel-time residuals at individual stations. It is also useful to check fully independent depth estimates, for example those from the centroid-moment-tensor analysis. If the problematic crustal model is detected, and it is not easy to find a better one, the near- and distant station effects should be decoupled (a two-step location): the epicenter is calculated from all stations, kept fixed, and the source depth is grid-search beneath the epicenter by means of the near stations. The ideas are applied to the Mw 5.2 Efpalio (Western Greece) earthquake of January 18, 2010, and the following aftershock sequence.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Bernard P., Lyon-Caen H., Briole P., Deschamps A., Boudin F., Makropoulos K., Papadimitriou P., Lemeille F., Patau G., Billiris H., Paradissis K., Castarede H., Charade O., Nercessian A., Avallone A., Zahradník J., Sacks S. and Linde A., 2006. Seismicity, deformation and seismic hazard in the western rift of Corinth: New insight from the Corinth Rift Laboratory (CRL). Tectonophysics, 426, 7–30.
Janský J., Zahradník J. and Plicka V., 2009. Shallow earthquakes: shallover than expected? Stud. Geophys. Geod., 53, 261–268.
Klein F.W, 2000. HYPOINVERSE Earthquake Location Program. http://earthquake.usgs.gov/research/software/#HYPOINVERSE
Klein F.W., 2002. User’s Guide to HYPOINVERSE-2000, a Fortran Program to Solve for Earthquake Locations and Magnitudes. U.S. Geological Survey Open-File Report 02-171, 123 pp.
Latorre D., Virieux J., Monfret T., Monteiller V., Vanorio T., Got J.-L. and Lyon-Caen H., 2004. A new seismic tomography of Aigion area (Gulf of Corinth, Greece) from the 1991 data set. Geophys. J. Int., 159, 1013–1031.
Lee W.H.K. and Valdés C.M., 1989. HYPO71PC. Toolbox for Seismic Data Acquisition, Processing, and Analysis. IASPEI Seismological Software Library, 1. IASPEI & SSA.
Lomax A., 2005. A reanalysis of the hypocentral location and related observations for the Great 1906 California earthquake. Bull. Seismol. Soc. Amer., 95, 861–877.
Lomax A., 2006. Probabilistic, Non-Linear, Global-SearchEarthquake Location in 3D Media. http://alomax.free.fr/nlloc/index.html
Lomax A. and Curtis A., 2001. Fast, probabilistic earthquake location in 3D models using oct-tree importance sampling. Geophys. Res. Abstr., 3, 955.
Lyon-Caen H., Papadimitriou P., Deschamps A., Bernard P., Makropoulos K., Pacchiani F. and Patau G., 2004. First results of the CRL seismic array in the western Corinth rift: evidence for old fault reactivation. C. R. Geosci., 336, 343–351.
Lyon-Caen H., Bernard P., Deschamps A., Lambote S. and Briole P., 2010. The January-February 2010 Pyrgos seismic swarm: a possible activation of the deep Psathopyrgos normal fault (western Corinth rift). http://www.esc2010.eu/cd/search/poster/n0051_T_SD1_P6_ID51_Lyon-Caen_H.html
Rigo A., Lyon-Caen H., Armijo R., Deschamps A., Hatzfeld D., Makropoulos K., Papadimitriou P. and Kassaras I., 1996. A microseismic study in the western part of the Gulf of Corinth (Greece): implications for large scale normal faulting mechanisms. Geophys. J. Int., 126, 663–688.
Serpetsidaki A., Sokos e., Tselentis G-A. and Zahradník J., 2010. Seismic sequence near Zakynthos Island, Greece, April 2006: Identification of the activated fault plane. Tectonophysics, 480, 23–32.
Sokos E. and Zahradník J., 2008. ISOLA — A Fortran code and Matlab GUI to perform multiplepoint source inversion of seismic data. Comput. Geosci., 34, 967–977.
Zahradník J., Janský J. and Plicka V., 2008a. Detailed waveform inversion for moment tensor of M∼4 events: Examples from the Corinth Gulf, Greece. Bull. Seismol. Soc. Amer., 98, 2756–2791.
Zahradník J., Gallovič F., Sokos E., Serpetsidaki A. and Tselentis A., 2008b. Quick fault-plane identification by a geometrical method: Application to the Mw 6.2 Leonidio earthquake, 6 January 2008, Greece. Seismol. Res. Lett., 79, 653–662.
Zollo A., De Matteis R., Capuano P., Ferulano F. and Innacone G., 1995. Constraints on the shallow crustal model of the Northern Appenines (Italy) from the analysis of mocroearthquake seismic records. Geophys. J. Int., 120, 646–662.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Janský, J., Novotný, O., Plicka, V. et al. Earthquake location from P-arrival times only: problems and some solutions. Stud Geophys Geod 56, 553–566 (2012). https://doi.org/10.1007/s11200-011-9036-2
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11200-011-9036-2