Teleseismic Data, Contribution from Greece

Abstract Teleseismic records from the Hellenic Unified Seismic Network for 815 events with magnitudes mb≥6, from 2011 to 2021, were thoroughly analyzed to provide the most comprehensive set of arrival-time picks and amplitude measurements. Analysis reveals a significant increase in observations compared with those reported to the International Seismological Centre (ISC), particularly for depth phases, S-type phases, and amplitudes used in broadband magnitude calculations. The short-period body-wave magnitudes (mb) presented in this study exhibit considerable scatter relative to those from the two main agencies, ISC and the National Earthquake Information Center. The magnitudes, especially for larger events, tend to be higher when derived from Greek stations. A key contributing factor to the scatter appears to be the inconsistent measurement of seismic wave periods as observed at ISC. In contrast, broadband surface-wave magnitudes (Ms) obtained from the present analysis show a near one-to-one correlation with the ISC standard Ms_20, indicating greater internal consistency. The use of broadband Ms is therefore recommended over the standard Ms_20 because it avoids the limitations associated with amplitude measurements in the 18–22 s period range, which is employed in approximately 85% of ISC Ms_20 readings. Broadband body-wave magnitudes (mB) are systematically higher than short-period mb values. However, due to the limited availability of comparable studies, no definitive conclusions can be drawn regarding this difference. A global map of surface-wave magnitude residuals Ms calculated per event reveals a consistent pattern that correlates well with the global surface-wave attenuation model, offering further support for its validity. This study shows that detailed teleseismic analysis by local networks improves local catalogues, reveals network-specific features, and contributes valuable data to global seismology. At the same time, it highlights the near absence of broadband magnitude usage, despite the IASPEI definition over 15 yr ago.