ISSN:
1365-246X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
On 1986 September 13 a magnitude 6.2 (Ms) earthquake occurred in the South Peloponnese (Greece) and severely damaged the town of Kalamata, In order to retrieve the acceleration levels recorded in Kalamata, synthetic accelerograms are computed. the source is modelled by an aggregate of circular shear-crack (barrier model) embedded, first in a two-layer crust model and second, in a structure taking into account a velocity gradient in the uppermost crust. Good agreement is found between the peak accelerations obtained from synthetics and those observed in Kalamata in the case of the gradient model. the model also predicts rapid variations (up to 50–60 per cent) of peak acceleration between stations spaced only 600 m apart. Therefore, the non-uniform repartition of damage observed in Kalamata may be explained, at least partly, as a source effect. Calculations also show that, because of the small distance between the fault plane and the stations, ground motion is dominated by the radiation of the closest sub-events and will depend on their stress-drop independently of the magnitude of the large event, Using a 2-D model, we also investigate the effects related to a north-south thickness variation of the surficial sedimentary deposits beneath the city. Expected peak spectral amplification is found to be relatively constant along the profile (about 3). However, the corresponding resonance frequency range is 2–4 Hz for the southern part of the city (where slight damage was observed) and 4–8 Hz for the northern part (from where heavy damage was reported). Simultaneous consideration of the largest aftershock strong motion records and of the aftershock distribution shows that the assumption concerning the average size of elementary subevent considered in the model is correct. Therefore, the rupture process on the Kalamata fault can be interpreted in terms of a barrier model.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-246X.1991.tb02502.x
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