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The most reliable of the globally available relative data have been used to derive empirical for mulas which relate the subsurface fault length,

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In the present article new predictive relations are proposed for the peak values of the horizontal components of ground acceleration, velocity, and displacement, using 619 strong motion recordings from shallow earthquakes in the broader Aegean area, which are processed using the same procedure in order to obtain a homogeneous strong motion database. The data set is derived from 225 earthquakes, mainly of normal and strike-slip focal mechanisms with magnitudes 4.5 Յ M Յ 7.0 and epicentral distances in the range 1 km Յ R Յ 160 km that have been relocated using an appropriate technique. About 1000 values of peak ground acceleration (PGA), velocity (PGV), and displacement (PGD) from horizontal components were used to derive the empirical predictive relations proposed in this study. A term accounting for the effect of faulting mechanisms in the predictive relations is introduced, and the UBC (1997) site classification is adopted for the quantification of the site effects. The new relations are compared to previous ones proposed for Greece or other regions with comparable seismotectonic environments. The regression analysis showed a noticeable (up to ϳ30%) variance reduction of the proposed relations for predicting PGA, PGV, and PGD values compared to previous ones for the Aegean area, suggesting a significant improvement of predictive relations due to the use of a homogeneous strong motion database and improved earthquake parameter information.

The preshock (critical) regions of 20 mainshocks with magnitudes between 6.4 and 8.3, which occurred recently (since 1980) in a variety of seismotectonic regimes (Greece, Anatolia, Himalayas, Japan, California), were identified and investigated. All these strong earthquakes were preceded by accelerating time-to-mainshock seismic crustal deformation (Benioff strain). The time variation of the cumulative Benioff strain follows a power law with a power value (m ‫ס‬ 0.3) in very good agreement with theoretical considerations. We observed that the dimension of the critical region increased with increasing mainshock magnitude and with decreasing long-term seismicity rate of the region. An increase of the duration of this critical (preshock) phenomenon with decreasing long-term seismicity rate was also observed. This spatial and temporal scaling expresses characteristics of the critical earthquake model, which are of importance for earthquake prediction research. We also showed that the critical region of an oncoming mainshock coincides with the preparing region of this shock, where other precursory phenomena can be observed.

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The Mw = 6.4 July 26, 2001 Skyros (North Aegean, Greece) earthquake struck the submarine western end of Northern Aegean Sea causing damage in the nearby Skyros Island. It occurred on a left‐lateral NW‐SE trending strike slip fault, oriented transverse to the dominant dextral strike‐slip faults that are present in the area, appearing to mark the boundary between them and the E‐W trending normal faults of the Greek mainland. Foreshock activity started 5 days before the mainshock, and intense aftershock activity followed on the main rupture plane and off fault. The seismogenic structure consists of three clusters with different orientation, independent from the known normal and dextral strike‐slip faults. Theoretical static stress changes from the main shock suggests off‐fault aftershock triggering, providing a tool for assessing the seismic hazard ensuing from strong aftershocks far from the main rupture.