Analyzing seismic activity to warn against terrorist activity

Ground movement tests recorded on October 7 by a Tel Aviv University Team the university announced Thursday that it has identified the potential to use seismic data for early warning of future terrorist activities.

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

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

The research was supported by grants from the Observatoire de la Côte d’Azur, the Israel Science Foundation, and the Israeli Minister of Energy and Infrastructure.

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

Dr. Asaf Inbal (source: TAU)

Forensic seismology

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

The team believes the study shows the potential of using seismic sensor technology for early warning of terrorist activity, but highlighted the possibility of retroactively identifying movements in Gaza months later.

The nationwide network of seismometers operated by the Israel Geological Survey is primarily intended to detect and locate earthquakes, Inbal explained, as well as to warn of strong tremors caused by high-magnitude seismic events. On the morning of October 7, 2023, “unusual levels of seismic noise were recorded” at three stations.

“This noise can certainly be attributed to vehicle traffic in Gaza as Hamas terrorists gathered for the attack,” Inbal said. “The time frame was between 6:00 a.m. and 6:30 a.m. before the rocket fire began. The probability that the recorded signals originate from Gaza is over 99.9%.

The introduction to the research paper notes that the low levels of background noise – due to Saturday being a quiet bank holiday and the date coinciding with the eve of Simchat Torah – and the large-scale mobilization in Gaza “suggest that some of the broadband stations “IS could register a mobilization signal even though they were dozens of kilometers from the Gaza Strip.”

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“The characteristics of the noise coming from Gaza and captured by Israeli stations are fundamentally different from the noise recorded at the same stations on previous Saturdays at these times,” he said.

Analysis of data from years

The team analyzed three years of data – recorded during the same time frame as the preceding attack – from three stations and found no Saturday morning in which correlated amplitudes were recorded at all three stations for more than 10 minutes, the study said in a statement.

Research conclusions. (Source: TAU)

“It is important to note that these stations are widely distributed and each station is primarily sensitive to seismic noise generated by nearby human activities,” Inbal said.

“For example, the distance between Ktsiot and Amazia is approximately 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 station was minimal, we found unique, widespread seismic amplitudes that monotonically increased with time before 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 an outdoor music festival near Re’im generated 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 7.”

The statement said the detected seismic noise began at 6 a.m. and intensified as the attack approached, with at times the noise containing short bursts strong enough to locate the source and track its progress. In the 30 minutes prior to the attack, the location and intensity of sources in Gaza suggest vehicle traffic moving south and north within Gaza.

“We have a good solution for the Salah al-Din road, the main traffic artery that crosses Gaza from Rafah in the south to Beit Lahia in the north,” he said. “We can confirm with a high degree of certainty that their forces were traveling along this route at speeds of between 25 and 50 km/h.”

“Observations from stations located several dozen kilometers from the Gaza border indicate convoys of heavy vehicles, such as bulldozers and trucks, carrying agents,” 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 to receive signals from central Gaza, near Nuseirat. “We know that the attack began almost simultaneously across the entire border, so these seismic observations provide further evidence of the extensive deployment of Hamas forces, possibly enabling a simultaneous breach of the ground barrier.”

Inbal expressed hope that the new knowledge will lead to wider use of such tools for security and industrial purposes.

“We see that graduates of the Department of Geophysics at Tel Aviv University are playing a leading role in scientific and technological progress, 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.