Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Acta Geophysica Polonica

2 2004

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: foreshocks

Sortuj według:

Ogranicz wyniki do:

Stress release during earthquake sequences

Gibowicz S.

Acta Geophysica Polonica

2004

Vol. 52, nr 3

271-299

The average stress drop and apparent stress released during 65 complex earthquake sequences from all over the world are estimated separately for foreshocks, main shocks and aftershocks. All of them but one occurred between 1977 and 1997. The Harvard CMT solutions are available for 60 main shocks, 38 foreshocks and 218 aftershocks. The stress drop is estimated using the values of seismic moment and source half duration and the scaling relations between various source parameters: seismic moment, source half duration, fault surface and fault length, taken from Harvard catalogues and other publications. The average stress drop is the highest during foreshocks (1.8 MPa), middle during main shocks (1.1 MPa) and the lowest during aftershocks (0.4 MPa). Similarly, the apparent stress, estimated from seismic moment and radiated energy taken from PDE-NEIC bulletins and other publications, is also the highest for foreshocks (0.6 MPa), middle for main shocks (0.4 MPa) and the lowest for aftershocks (0.2 MPa).

A search for sequences of mining-induced seismic events at the Rudna Copper Mine in Poland

Kwiatek G.

Acta Geophysica Polonica

2004

Vol. 52, nr 2

155-171

A detailed analysis of the Rudna copper mine's seismic catalogue for 1980-2003, with a threshold local magnitude ML> 1.3, allowed to distinguish several types of event sequences related to 345 stronger mining events of magnitude greater than 3.0. Events without aftershocks and foreshocks were observed as well as those where the number of aftershocks numbered more than ten, while foreshocks - several. Foreshocks were recorded for 58 events, nearly all of them several tens of minutes before the main seismic event. Aftershocks accompanied the 190 strongest events; the greatest number of aftershocks was 10 for an event of magnitude just over 3.0. For the two strongest events, of magnitudes ML = 4.1 and ML = 4.2, the number of aftershocks was radically different, 9 and 1, respec-tively. Different numbers of aftershocks were observed depending on the loca-tion of the main event in various mining areas, which is related to the differences in the seismicity of individual zones within the mine. Non-parametric probability distribution functions of magnitude have been determined for the different seismogenic zones. In addition, the value of the b coefficient of the Gutenberg-Richter relation has been analyzed for each zone. These studies confirmed that seismicity varies within the mine.