Abstract
Teleseismic body wave modelling, time domain moment tensor inversion of regional waveforms and spectral analysis of the far-field P-wave pulses are used to derive the source parameters of the July 26, 2001 Skyros earthquake (M 6.5). Its epicentre is located south of the Sporades Islands in the North Aegean Sea (Greece). Previous focal mechanism solutions indicate motion on strike-slip faults. The time domain moment tensor inversion is applied for the first time to the regional waveforms of the recently established broadband network in Greece. Its application gave results which are highly consistent with teleseismic waveform modelling. The results of this study, in combination with the distribution of aftershocks, indicate left-lateral strike slip motion on a NW-SE striking fault with parameters: fault plane (strike = 151°, dip = 83°, rake = 7°) and auxiliary plane (strike = 60°, dip = 84°, rake = 173°), depth 12 km and M 0 = 5.98e18 Num. Moreover, the time domain moment tensor inversion technique yielded a pure double couple source with negligible CLVD. The spectral analysis of the far-field P-wave pulses resulted in a fault length L ~ 32 km, stress drop 6m ~ 9 bars and average displacement u ~ 30 cm. These values are in very good agreement with those estimated from empirical scaling relations applicable to the Aegean area.
Highlights
On July 26, 2001 an earthquake of M 6.5 occurred in the Aegean Sea, a few kilometres NW of the island of Skyros
We use teleseismic data from the Global Seismograph Network (GSN) as well as regional broadband waveforms recorded by the recently installed broadband network operated by the National Observatory of Athens (NOA)
We found that the employed velocity model works very well for stations ATH, PRK and APE, it is inadequate for the rest of the epicentre-station paths
Summary
On July 26, 2001 an earthquake of M 6.5 occurred in the Aegean Sea, a few kilometres NW of the island of Skyros (fig. 1). On July 26, 2001 an earthquake of M 6.5 occurred in the Aegean Sea, a few kilometres NW of the island of Skyros Despite its large magnitude and the fact that it was felt in a wide region, the earthquake did not cause extensive damage as its epicentre was located at sea (38.995°N, 24.382°E; Geophysical Laboratory, Aristotle University of Thessaloniki). Limited damage was only observed in the island of Skyros, concerning mainly old residential buildings, a 1000-year-old monastery located inside the island’s castle and limited landslides and rock falls. We use teleseismic data from the Global Seismograph Network (GSN) as well as regional broadband waveforms recorded by the recently installed broadband network operated by the National Observatory of Athens (NOA). The focal mechanism and related parameters are determined through a comparative application of two different methodologies: teleseismic waveform modelling (Nábelek, 1984) and time
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