Article | Open | Published:
Relocation of large intermediate-depth earthquakes in the Vrancea region, Romania, since 1934 and a seismic gap
Earth, Planets and Spacevolume 60, pages565–572 (2008)
We relocated M 6 or larger intermediate-depth earthquakes in Vrancea, Romania that have occurred since 1934. To determine their absolute hypocenters accurately, we combined them with recent (from January 1996 to November 2003) smaller earthquakes recorded by the Romanian local network and then relocated all of them simultaneously using a modified joint hypocenter determination method. Using the data on recent small earthquakes we first obtained an estimate of the dimensions of the active seismic region of intermediate-depth earthquakes: length, 85 km; along a NE-SW direction; width, 20 km; depth 60-160 km. We then determined that the 1940 (M 7.7), 1977 (M 7.5) and 1990 (M 6.9) major earthquakes were located near the NE edge of the seismic region, while the 1986 (M 7.2) was located inside the seismic region. The focal depths of the 1940, 1977, 1986 and 1990 major earthquakes were calculated to be 124, 98, 135 and 84 km, respectively and their source areas to range from 60 to 140 km in depth. The only unbroken area is at a depth of 140–160 km, which we current consider to be a seismic gap. Based on the regularity of past large earthquakes, we propose that the next M 7 intermediate-depth earthquake can be expected to occur in Vrancea at a depth interval of 140–160 km sometime early in this century.
Douglas, A., Joint epicenter determination, Nature, 215, 47–48, 1967.
Dziwonski, A. M., T.-A. Chou, and J. Woodhouse, Determination of earthquake source parameters from waveform data for studies of global and regional seismicity, J. Geophys. Res., 86, 2825–2852, 1981.
Enescu, D. and B. D. Enescu, Focal mechanism, global geophysical phenomena and Vrancea (Romania) earthquake prediction, Rev. Roum. Geophys., 40, 11–31, 1996.
Enescu, D. and B. D. Enescu, Possible cause-effect relationships between Vrancea (Romania) earthquakes and some global geophysical phenomena, Natural Hazards, 19, 233, 1999.
Enescu, D., V. Marza, and I. Zamarca, Contributions to the statistical prediction of Vrancea earthquakes, Rev. Roum. Geophys., 18, 67, 1974.
Fedotov, S. A., Regularities of the distribution of strong earthquakes in Kamchatka, the Kurile Islands and northeastern Japan, Acad. Sci. USSR Trudy Inst. Physics Earth, 36, 1965.
Freedman, H. W., A statistical discussion of P residuals from explosions, Part 2, Bull. Seismol. Soc. Am., 57, 545–561, 1967.
Frohlich, C., Deep earthquakes, Cambridge Uni. Press, 2006.
Fuchs, K., K.-P Bonjer, G. Bock, I. Cornea, C. Radu, D. Enescu, D. Jianu, A. Nourescu, G. Merkler, T. Moldoveanu, and G. Tudorache, The Romanian earthquake of March 4, 1977, II. Aftershocks and migration of seismic activity, Tectonophysics, 53, 225–247, 1979.
Hartzell, S., Analysis of the Bucharest strong ground motion record for the March 4, 1977 Romanian earthquake, Bull. Seismol. Soc. Am., 69, 513–530, 1979.
Headquarters for Earthquake Research Promotion, http://www.jishin.go.jp/main/index-e.html, 2007.
Hurukawa, N., Quick aftershock relocation of the 1994 Shikotan earthquake and its fault planes, Geophys. Res. Lett., 22, 3159–3162, 1995.
Hurukawa, N. and M. Imoto, Subducting oceanic crusts of the Philippine Sea and Pacific plates and weak-zone-normal compression in the Kanto district, Japan, Geophys. J. Int., 109, 639–652, 1992.
Imoto, M. and N. Hurukawa, Assessing potential seismic activity in Vrancea, Romania, using a stress-release model, Earth Planets Space, 58, 1511–1514, 2006.
International Seismological Centre, On-line Bulletin, http://www.isc.ac.uk/Bull, Internatl. Seis. Cent., Thatcham, United Kingdom, 2006.
Iosif, T., M. C. Oncescu, and S. Iosif, March 4, 1977 Vrancea earthquake, spatial distribution of events and temporal evolution of focal mechanism, Bull. Int. Inst. Seismol. Earthq. Eng., 20, 1–18, 1983.
Monfret, T., A. Deschamps, and B. Romanowicz, The Romanian earthquake of August 30, 1986: A study based on GEOSCOPE very long-period and broadband data, Pageoph, 133, 367–379. 1990.
Muller, G., K.-P. Bonjer, H. Stockl, and D. Enescu, The Romanian earthquake of March 4, 1982, I. Rupture process inferred from fault-plane solution and multiple-event analysis, J. Geophys., 44, 203–218, 1978.
Oncescu, M. C, Investigation of a high stress drop earthquake on August 30, 1986 in the Vrancea region, Tectonophysics, 163, 35–43, 1989.
Oncescu, M. C. and K. P. Bonjer, A note on the depth recurrence and strain release of large Vrancea earthquakes, Tectonophysics, 272, 291–302, 1997.
Oncescu, M., V. I. Marza, M. Rizescu, and M. Popa, The Romanian earthquake catalogue between 1984–1997, in Vrancea Earthquakes: Tectonics, Hazard Risk Mitigation, edited by F. Wenzel et al., 43–47, 1999.
Purcaru, G., Quasi- and supercyclicity of earthquakes and time-magnitude gaps in earthquake prediction, Tech. Rep., NORSAR, Sci. Rep., No. 6-73/74, 53–55, 1974.
Purcaru, G., The Vrancea, Romania, earthquake of March 4, 1977—A quite successful prediction, Phys. Earth Planet. Inter, 18, 274–287, 1979.
Radulian, M. and C. I. Trifu, Would it have been possible to predict the August 30, 1986 Vrancea earthquake?, Bull. Seismol. Soc. Am., 81, 2498–2503, 1991.
Rakers, E. and G. Muller, The Romanian earthquake of March 4,1977, III. Improved Focal Model and Moment Determination, J. Geophys., 50, 143–150, 1982.
Sperner, B., D. Ioane, and R. J. Lillie, Slab behaviour and is surface expression: new insights from gravity modeling in the SE-Carpathians, Tectonophysics, 382, 51–84, 2004.
Sykes, L. R., Aftershock zones of great earthquakes, seismicity gaps, and earthquake prediction for Alaska and the Aleutians, J. Geophys. Res., 76, 8021, 1971.
Wortel, M. J. R. and W. Spakman, Subduction and slab detachment in the Mediterranean-Carpathian region, Science, 290, 1910–1917, 2000.