Abstract
The Mediterranean tsunami warning system is based on national monitoring centers (Tsunami Service Providers, TSPs) and operates under the IOC/UNESCO umbrella. For the first time we evaluate in depth the system’s performance for improving its operational effectiveness in conditions of extremely narrow time frames due to the near-field tsunami sources. At time 10 (± 2) min from the origin time, to, of the 2 May 2020 (Mw6.6) earthquake in Crete, the Greek, Italian and Turkish TSPs sent alerts to civil protection subscribers. A small tsunami (amplitude ~16 cm a.m.s.l.) of magnitude Mt6.8, arriving at south Crete in ~17 min from to, was documented from tide-gauge records and macroscopic observations. The analysis of the upstream alert messages showed that the tsunami alert efficiency is not adequate, since (1) earthquake parameters of low accuracy were used for the initial message, (2) alerts were issued after some forecasted wave arrival times had expired, (3) alert messages are characterized by various discrepancies and uncertainties. Our calculations showed that the upstream component improves if the alert time is shortened by a few minutes and the initial earthquake parameters are more accurate. Very late procedures were noted in the Greek civil protection downstream component, thus rendering response actions useless. In Israel, a bit more time was available to the authorities for decision making. A drastic improvement of the downstream component is needed to achieve timely alerting for local authorities and communities.
Highlights
Near-field tsunamis produced in subduction zones arrive at the closest coasts in tenths of minutes or less [1], leaving very little time for early warning
For the local tsunami that followed, the 2 May 2020 earthquake (Mw = 6.6) to the south of Crete in the Hellenic Subduction Zone (HSZ), Greece (Figure 1), data are available for both the upstream and downstream components of the warning system, and, this case offers a good opportunity to evaluate the operational performance of both components. To this aim we present the main observations regarding the 2020 earthquake and tsunami, analyze the operational efficiency of the upstream component of the system based on a series of alert messages issued by three Tsunami Service Providers (TSPs), examine the downstream component focusing on the civil protection response in Greece and in Israel and discus realistic perspectives for improving the tsunami alert efficiency
Based on the forecasts contained in the alert messages issued by three TSPs after the earthquake, we examine in tsunami forecasts contained in the alert messages issued by three TSPs after the earthquake, we depth the tsunami alert efficiency for the first time in the North-East Atlantic and Mediterranean Tsunami Warning System (NEAMTWS) history
Summary
Near-field tsunamis produced in subduction zones arrive at the closest coasts in tenths of minutes or less [1], leaving very little time for early warning. Subduction Zone (HSZ) marks the convergence lithospheric plate boundary between the Nubian (African) plate and the southern margin of the Eurasian plate where the former subducts underneath the later (Figure 1a). On 2 May 2020 a strong earthquake with a moment magnitude Mw = 6.6 ruptured to the south of Crete, in the Hellenic Subduction Zone (HSZ) (Figure 1a). The earthquake epicenter was located at a distance of ~90 km from the closest coast of Crete, which implies that it was a very near-field source for tsunami generation. According to the alerting protocols adopted within the GeoHazards 2020, 1, 44–60; doi:10.3390/geohazards1010005 www.mdpi.com/journal/geohazards
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