On October 26, 2024, the Israeli Defence Forces (IDF) triggered an explosion of 370 T in an underground Hezbollah facility in southern Lebanon, ~1 km off the Israeli border, generating a seismic moment equivalent to a M3.6 earthquake. Four seconds after detonation, the Geological Survey of Israel’s (GSI) Earthquake Early-Warning System, Truaa, identified the explosion as a M5.2 event, mislocating the epicentre by ~25 km. Since this exceeded Truaa's warning threshold (M4.5), an alert was automatically sent by the IDF’s Home Front Command systems up to an epicentral distance of 94 km. Seven seconds after detonation, the location and magnitude estimates were updated and stabilized to the actual location, and to a magnitude below the warning threshold.

We found that the Truaa system operated as designed and that the magnitude overestimation resulted from an unusually large explosion, short epicentral distances, and to mislocation due to a depth fixed at 8 km in Truaa's location algorithm.

Real-time discrimination between earthquakes and explosions is still considered a research challenge not yet accomplished; it is a goal that is being explored in our research team. Similarly, the Truaa EEW system algorithm, EPIC, cannot discriminate between explosions and earthquakes. Therefore, we examined and tested several manual procedures, to prevent the alerting of such scheduled explosions. Some of these new measures are now part of the GSI’s procedures.

As a result, we found no grounds to modify the operational configuration of Truaa.