| More


Views: 86 Downloads: 71
E. Sokos, V.E. Pikoulis, E.Z. Psarakis, A. Lois
E. Sokos, V.E. Pikoulis, E.Z. Psarakis, A. Lois


A series of strong earthquakes took place at the Trichonis lake area, during April 2007. Three events, with M~5.0 occurred within one day, causing damages to almost all nearby villages and especially at the small town of Thermo. The sequence lasted for more than one month with small to moderate size events. It was recorded by regional networks and results related to its time and space evolution have already been published. Just after the major events a microseismic network was deployed in the area, by the University of Patras, Seismology Laboratory. Eight stations were installed, with short period, three component sensors and portable digital recorders. The network was in operation for a period of one month and a lot of events were recorded by enough stations to provide a reliable location. We present here the analysis of these data using modern methodologies like waveform cross-correlation techniques and further relocation of the events using waveform based differential time. The results partially support the findings of the regional networks, as regards the gross characteristics of the aftershock sequence, but provide an enhanced description of it. The space time evolution of the aftershock sequence reveals the activation of more than one fault in the area and suggests the connection of the sequence with an unmapped fault.


Trichonis Lake; seismotectonics; relocation; double-difference; clustering algorithms; graph partitioning; cross-correlation;

Full Text:



Bardaine T., Gaillot P., Dudos-Sallee N., Blanco J., Senechal G. 2006. Characterization of Seismic Waveforms

and Classification of Seismic Events Using Chirplet Atomic Decomposition. Example from

the Lacq Gas Field (Western Pyrenees, France). Geophys. J. Int., 166, pp 699-718.

Becker D., T. Meier, M. Rische, M. Bohnhoff, H.P. Harjes. 2006. Spatio – temporal microseismicity clustering

in the Cretan region. Tectonophysics, 423, pp 3 – 16, 2006.

Cocard, M., Kahle, H.-G., Peter, Y., Geiger, A., Veis, G., Felekis, S., Paradissis, D., Billiris, H., 1999.

New constraints on the rapid crustal motion of the Aegean region: recent results inferred from GPS

measurements (1993–1998) across the West Hellenic Arc, Greece. Earth and Planetary Science Letters

, 39–47.

Doutsos, T., Kontopoulos, N., Frydas, D., 1987. Neotectonic evolution of northwestern continental Greece.

Geol. Rundsch. 76, 433–450.

Doutsos, T., Kokkalas, S., 2001. Stress and deformation patterns in the Aegean region. Journal of Structural

Geology 23, 455–472.

Evangelidis C. P., Konstantinou K. I., Melis N. S., Charalambakis M., Stavrakakis G. N., 2008, Waveform

relocation and focal mechanism analysis of an earthquake swarm in Trichonis lake, western

Greece, Bull. Seism. Soc. Am. 98(2), pp. 804-811.

Everitt, B. S., Landau S., Leese M. Cluster Analysis ( fourth edition). Arnold, London, 2001.

Fréchet, J., 1985. Sismogenèse et doublets sismiques. Thèse d’État, Université Scientifique et Médicale

de Grenoble, 206 pp.

Got, J.-L., Fréchet, J., Klein, F.W., 1994. Deep fault plane geometry inferred from multiplet relative location

beneath the south flank of Kilauea. J. Geophys. Res. 99, 15375–15386.

Haslinger, F., Kissling, E., Ansorge, J., Hatzfeld, D., Papadimitriou, E., Karakostas, V., Makropoulos, K.,

Kahle, H.G., Peter, Y., 1999. 3D crustal structure from local earthquake tomography around the Gulf

of Arta (Ionian region, NW Greece). Tectonophysics 304, 201–218.

Kiratzi, A., Sokos, E., Ganas, A., Tselentis, A., Benetatos, C., Roumelioti, Z., Serpetsidaki, A., Andriopoulos,

G., Galanis, O., Petrou, P., 2008. The April 2007 earthquake swarm near Lake Trichonis and

implications for active tectonics in western Greece, Tectonophysics 452, 51- 65.

Klein, F.W., 2002. User’s guide to HYPOINVERSE-2000, a FORTRAN program to solve earthquake locations

and magnitudes. U. S. Geological Survey Open File Report 02- 606, Version 1.0.

Lee, W. H. K., R. E. Bennett, and K. L. Meagher, 1972. A method of estimating magnitude of local earthquakes

from signal duration, Open File Report, U. S. Geological Survey, 28 pp.

Lee, W.H.K. and J.C. Lahr, 1975. HYPO 71: A computer program for determining hypocenter, magnitude,

and first motion pattern of local earthquakes. USGS Open file report, p75-311.

Lee, W. H. K. and C. M. Valdes, 1985. HYP071PC: A personal computer version of the HYPO71 earthquake

location program, U. S. Geological Survey Open File Report 85-749, 43 pp.

Lomax, A.J., 1991. User Manual for SeisGram. In Digital Seismogram Analysis and Waveform Inversion,

IASPEI Soft ware Library Volume 3, W.H.K. Lee, ed., Seismological Society of America.

Melis, N.S., Brooks,M., Pearce, R.G., 1989.Amicroearthquake study in the Gulf of Patras region, westXLIII,

No 4 – 2191

ern Greece, and its seismotectonic interpretation. Geophys. J. Int. 98, 515–524.

Paige C. C. and. Saunders M. A, 1982. LSQR: An algorithm for sparse linear equations and sparse least

squares, TOMS 8(1), 43-71.

Papazachos, C.B., Kiratzi, A.A., 1996. A detailed study of the active crustal deformation in the Aegean

and surrounding area. Tectonophysics 253, 129–153.

Pikoulis V.E., Psarakis E.Z., Sokos E.N. 2006. A New Two Step Correlation Based Technique for the

Classification of Seismic Events. Poster Section of First European Conference on Earthquake Engineering

and Seismology, Geneva, Sept.

Pikoulis V.E., Psarakis E.Z. and Sokos E.N. A Novel Seismic Data Processing Technique for the Event

Relocation Problem. Bulletin of the Seismological Society of America (to be submitted).

Psarakis E. and Evangelidis G. 2005. An Enhanced Correlation-Based Method for Stereo Correspondence

with Sub-Pixel Accuracy. Proc. of Inter. Conference on Computer Vision, ICCV05, pp.907-912,


Roumelioti, Z., A. Kiratzi and N. Melis, 2003. Relocation of the July 26, 2001 Skyros island (Greece)

earthquake sequence using the double-difference technique, Physics of the Earth and Planetary Interior,

Vol. 138, 231 - 239.

Waldhauser, F., , 2001. HypoDD: A computer program to compute double-difference hypocenter locations,U.S.

Geol. Surv. open-file report, 01-113, Menlo Park, California.

Waldhauser, F., Ellsworth, W.L., 2000. A double-difference earthquake location algorithm: method and

application to the Northern Hayward fault, California. Bull. Seismol. Soc. Am. 90, 1353–1368.

Wells, D.L., Coppersmith, K.J., 1994. New empirical relationships among magnitude, rupture length,

rupture width, rupture area, and surface displacement. Bull. Seismol. Soc. Am. 84, 974–1002.


  • There are currently no refbacks.

Copyright (c) 2017 E. Sokos, V.E. Pikoulis, E.Z. Psarakis, A. Lois

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.