Toward a multi-hazard earthquake–tsunami early warning system: a feasibility study

For coastal areas located close to offshore seismic sources, earthquake risk is inherently multi-hazard: intense ground shaking and tsunami inundation can occur in rapid succession, with very short lead times for protective actions. In these near-field settings, traditional Tsunami Early Warning Systems (TEWS), which rely on seismic source parameters available several minutes after origin time, may provide alerts that are only marginally earlier than tsunami arrival, limiting their effectiveness.

In this study, we evaluate the integration of rapid earthquake magnitude and location estimates from QuakeUp, an impact-based Earthquake Early Warning System (EEWS), into a tsunami early warning workflow. QuakeUp processes real-time seismic observations to issue initial earthquake alerts within a few seconds, based on fast estimates of magnitude, location, and potential damage zone, supporting immediate risk mitigation for ground shaking. These estimates are then simultaneously used to initialize Probabilistic Tsunami Forecasting (PTF), enabling a coordinated multi-hazard warning strategy in which earthquake and tsunami risks are addressed within a unified, time-critical framework.

We present a real test case to quantify the earliness and accuracy of EEWS-derived source parameters and assess their impact on tsunami forecasting. A hindcast of the 30 October 2020 Mw 7.0 Aegean Sea earthquake, whose tsunami reached nearby coastlines in approximately 10 minutes, shows that the EEWS delivers stable and accurate hypocenter and magnitude estimates about 40 seconds after origin time. These estimates are comparable to those provided by the operational Early-Est system, which become available only after several minutes in the Mediterranean region. When used to initialize a PTF procedure, the EEWS-based source characterization yields coastal runup estimates in reasonable agreement with observations, despite the substantially reduced warning latency.

To further assess the robustness of the results obtained in the real case, we analyze a second scenario based on 150 simulated seismogram datasets for earthquakes in the Messina Strait (Southern Italy), a region characterized by high exposure and extremely short tsunami travel times. For events with moment magnitudes between 6.0 and 7.0, the analysis confirms that the integrated EEWS–TEWS workflow can provide reliable source estimates within one minute, supporting its applicability to near-field tsunami early warning. 

This study provides the first demonstration of a combined EEWS–TEWS approach for near-coastal tsunamigenic events, highlighting its potential for dual risk mitigation within a multi-hazard early warning perspective. Future work will focus on testing performance in an operational setting, including the effects of network latencies and configuration-dependent efficiency. In addition, the EEWS technique employed, by providing a preliminary mapping of the most damaged zone, offers a promising perspective for extracting early constraints on seismic source geometry. This information could further reduce uncertainty in near-field tsunami inundation forecasts.