TAU discovers potential use of seismic activity to warn of terrorist activity 

Research of ground motions recorded on October 7 by a Tel Aviv University team has identified the potential of using seismic data to provide an early warning for future terrorist activities, the university announced on Thursday. 

"The results show that on the morning of October 7, seismic stations located in southern Israel detected weak ground motions caused by the unusual movement of heavy vehicles (e.g., tractors, bulldozers, and trucks) within the Gaza Strip,” the researchers stated. 

The research article, titled, “Forensic Seismic Evidence for Precursory Mobilization in Gaza Leading to the October 7 Hamas Attack,” was published in The Seismic Record, a peer-reviewed journal of the Seismological Society of America.

An Observatoire de la Côte d’Azur grant, an Israeli Science Foundation grant, and the Israeli Minister of Energy and Infrastructure supported the research. 

Led by Dr. Asaf Inbal, researchers from the Department of Geophysics at TAU's Porter School of the Environment and Earth Sciences and Sackler Faculty of Exact Sciences analyzed data recorded at three Israeli Seismic Network (IS) stations, located in Amazia, Ktsiot, and Yatir in southern Israel. The stations are located between 30 and 50 kilometers (18 to 31 miles) from Gaza. 

Forensic seismology

Forensic seismology is generally used to monitor conventional and nuclear explosions, the researchers explained, and they said this is the first time that “weak ground motions resulting from preparations for a terrorist attack have been identified by analyzing the characteristics of seismic noise induced by vehicular traffic.” 

The team believes the research demonstrates the potential of using seismic-based sensing technology to provide early warnings of terrorist activity, but they emphasized the months-later, retroactive identification of the movements in Gaza. 

The nationwide network of seismometers operated by the Israeli Geological Survey is primarily designed to detect and locate earthquakes, explained Inbal, and to provide warnings of strong shaking caused by large-magnitude seismic events. On the morning of October 7, 2023, the three stations “recorded unusual seismic noise levels.” 

“This noise can be attributed with confidence to the vehicular activity in Gaza as Hamas terrorists gathered for the attack,” Inbal said. “The time frame was between 6:00 and 6:30 AM, before the rocket fire began. The likelihood that the recorded signals originated from Gaza is over 99.9%."

The research article introduction notes that the low background noise levels—due to Saturday being a quiet, off-work day and the date coinciding with the eve of the Simchat Torah holiday—and the large-scale mobilization in Gaza “suggest that some of the IS broadband stations may have recorded the mobilization signal despite being located tens of kilometers from the Gaza Strip.”

“The characteristics of the noise originating from Gaza and captured by the Israeli stations are fundamentally different from those recorded at the same stations on previous Saturdays during those hours,” he said. 

Analyzing years of data

The team analyzed three years of data—recorded in the same time frame as the one leading up to the attack—from the three stations and found no Saturday morning when correlated amplitudes were recorded at all three stations for more than 10 minutes, according to the statement. 

“It's important to note that these stations are widely spaced, with each station primarily sensitive to seismic noise generated by nearby human activity,” Inbal said.

“For instance, the distance between Ktsiot and Amazia is about 80 kilometers, and on previous Saturdays, there was no correlation between the data recorded at these stations. On the morning of the attack, when local activity near the stations was minimal, we found unique widespread seismic amplitudes, which monotonically increased with time approaching the attack.”

“No known natural or human source on the Israeli side could have generated seismic signals with a distribution and intensity similar to those attributed to Hamas movements,” he added.

“Although the outdoor music festival near Re'im generated some seismic noise, our analysis shows that this noise does not match the strength or location of the noise sources recorded by the Israeli seismic network on October 7th."

Analysis indicates the detected seismic noise started at 6 a.m. and intensified as the attack approached, according to the statement, and the noise would occasionally contain short bursts strong enough to pinpoint the source and track the progress. In the 30 minutes leading to the attack, the location and intensity of the sources in Gaza suggest vehicular movements advancing southward and northward within Gaza. 

"We have good resolution along Salah al-Din Road, a major thoroughfare crossing Gaza from Rafah in the south to Beit Lahia in the north," he said. "We can confirm with high certainty that their forces moved along this route at speeds of 25 to 50 km/h.”

“Observations from stations dozens of kilometers from Gaza's border indicate convoys of heavy vehicles such as bulldozers and trucks carrying operatives,” Inbal added.

“Three minutes before the attack began, we detected noise sources reaching the northern end of Gaza near Beit Lahia and the southern end near Khan Yunis. At the same time, we continued receiving signals from central Gaza, near Nuseirat. We know the assault began almost simultaneously along the entire border, so these seismic observations provide further evidence of the extensive deployment of Hamas forces, likely enabling the simultaneous breach of the ground barrier." 

Inbal said he hopes the new knowledge will lead to expanded use of such tools for security and industrial purposes. 

“We see graduates of the Department of Geophysics at Tel Aviv University playing a leading role in scientific and technological advancements, and we are confident that in the future, multi-purpose seismic-sensing technologies will be more widely used in various fields that impact our daily lives," he concluded.