The instability of the M (W) and M (L) comparison for earthquakes in Greece for the period 1969 to 2007

作者：Roumelioti Zafeiria; Kiratzi Anastasia^*; Benetatos Christoforos

来源：Journal of Seismology, 2010, 14(2): 309-337.

DOI：10.1007/s10950-009-9167-x

• Magnitude
• Local magnitude
• Moment magnitude
• Aegean
• Earthquake

We use 576 earthquakes of magnitude, M (w), 3.3 to 6.8 that occurred within the region 33A degrees A N-42.5A degrees A N, 19A degrees A E-30A degrees A E in the time period 1969 to 2007 to investigate the stability of the relation between moment magnitude, M (w), and local magnitude, M (L), for earthquakes in Greece and the surrounding regions. We compare M (w) to M (L) as reported in the monthly bulletins of the National Observatory of Athens (NOA) and to M (L) as reported in the bulletins of the Seismological Station of the Aristotle University of Thessaloniki. All earthquakes have been analyzed through regional or teleseismic waveform inversion, to obtain M (w), and have measured maximum trace amplitudes on the Wood-Anderson seismograph in Athens, which has been in operation since 1964. We show that the Athens Wood-Anderson seismograph performance has changed through time, affecting the computed by NOA M (L) by at least 0.1 magnitude units. Specifically, since the beginning of 1996, its east-west component has been recording systematically much larger amplitudes compared to the north-south component. From the comparison between M (w) and M (L) reported by Thessaloniki, we also show that the performance of the sensors has changed several times through time, affecting the calculated M (L)'s. We propose scaling relations to convert the M (L) values reported from the two centers to M (w). The procedures followed here can be applied to other regions as well to examine the stability of magnitude calculations through time.

• 出版日期2010-4