A strong earthquake struck Semnan in northern Iran early Friday, rattling a region fraught with tensions. The 5.1-magnitude shallow earthquake caused concern because it struck near a city with a space and missile complex.

The region remained tense both geologically and politically. The shallow earthquake, 10 kilometres deep, triggered an alarm. According to The Times of Israel, there are no immediate reports of damage or casualties.

The earthquake occurred about 35 kilometres southwest of Semnan, near Tehran, in central Iran. It struck at 7:49 UTC, according to the report. At the time of the quake, tensions were already high due to Iran's ongoing conflict with Israel.

The Semnan Space Centre and the Semnan Missile Complex, run by Iran’s military, were located in Semnan.

Iran was one of the most earthquake-prone countries in the world. It sat on the Alpine-Himalayan seismic belt, which is geologically active. Its complex tectonic setting caused regular seismic activity. Over the years, many of these earthquakes have led to significant destruction and fatalities. Iran experiences about 2,100 earthquakes every year. Of those, 15 to 16 were magnitude 5.0 or higher.

Nuclear activities, especially underground nuclear explosions, trigger earthquakes by causing tectonic movements near the blast. The US Geological Survey (USGS) stated that such explosions could cause seismic events, but these remained much smaller in magnitude than the explosion itself and occurred within a few tens of kilometers from the blast site.

These quakes were generally less intense and caused fewer aftershocks than natural ones. Seismologists distinguished them by analysing wave patterns. Nuclear explosions produced mainly P-waves. Natural earthquakes generate both P and S-waves. The seismic waves from nuclear explosions differed from those of natural earthquakes.

The Berkeley Seismology Lab explained that nuclear test seismograms were dominated by compressional P-waves. Natural earthquakes generated strong S-waves as well. This distinction helped seismologists tell the two apart. They used moment tensor solutions, as described by National Geographic, to trace waves back to their source and identify the cause of the shaking.

On June 15, a 2.5-magnitude earthquake occurred near Fordo. It happened at the same time as military activity. However, expert analysis, including from the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO), confirmed the event matched natural seismic patterns.

Earlier events showed the same scientific consistency. During the four-day India-Pakistan conflict in May, tremors were recorded in Pakistan. At that time, a theory of atomic activity also emerged. Experts reviewed the facts using seismographic evidence and confirmed the quakes were natural.

Using these scientific explanations, experts concluded that nuclear explosions could cause small, local earthquakes. The latest seismic events in Iran near nuclear facilities aligned with natural tectonic activity, considering the region’s high seismic risk.

Expert assessments from CTBTO, USGS, and independent seismologists supported this conclusion. They dismissed claims of nuclear tests or military-induced earthquakes. The evidence pointed to natural causes. Still, they opined, continued monitoring and more research remained important, especially in conflict zones where speculation moved faster than the earthquake itself.