TEHRAN — A series of nine small earthquakes, including one of magnitude 4.6, struck the Pardis area east of Tehran overnight near the Mosha fault. The seismic activity did not cause casualties or material damage.

While tremors are frequent in the Pardis area, it is far less common for several to occur in succession. The tremors were felt close to the Mosha fault, one of Iran's most active seismic zones, which extends about 150 kilometers in length and runs approximately 40 kilometers from Tehran.

Tehran, a metropolitan area of more than 14 million people, lies near several major active faults, including the North Tehran fault, the Mosha fault and the Rey fault. Iran is among the world's most quake-prone countries. The 2003 Bam earthquake killed more than 30,000 people.

Seismologist Mehdi Zare addressed the question of what the cluster of tremors might signal for the region. "It was not clear whether the tremors represented a release of built-up seismic energy that would reduce future risk or instead were warning signs of stronger future activity along the fault system near Tehran," Zare said.

He also pointed to factors beyond the geology that shape the capital's exposure to seismic events. "Tehran's vulnerability is amplified not only by active fault lines but also by dense urban development, population concentration and limited preparedness," he said. "Even relatively small earthquakes can cause disruption in the capital due to fragile infrastructure and congestion, complicating emergency response."