The tremors have been felt in an area close to the Mosha fault, one of Iran’s most active seismic zones.

A series of nine small earthquakes struck the Pardis area east of Tehran overnight, Iran’s Mehr news agency reported on Wednesday, renewing fears among experts and residents that the Iranian capital could face a major seismic disaster.

The repeated activity has revived concerns that accumulated tectonic pressure beneath and around the capital, which lies close to several active fault lines, could at some point in the future trigger a much larger earthquake.

While tremors in the area are frequent, it is far less common for several to occur in succession.

The tremors, recorded over a single night in eastern Tehran province, were felt in an area close to the Mosha fault, one of Iran’s most active seismic zones.

The fault, about 150km (93 miles) in length, is one of the major active faults of the country, located approximately 40km (25 miles) from the capital.

No casualties or damage

State media reported that the magnitude of one of the earthquakes was 4.6, but the mild seismic activity did not cause casualties or material damage.

Semi-official Mehr news agency quoted seismologist Mehdi Zare as saying 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 warned that 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.

Tehran, a metropolitan area of more than 14 million people, lies near major active faults, including the North Tehran, Mosha and Rey.

Iranian experts have repeatedly warned that a major earthquake near Tehran could have catastrophic consequences.

Iran is among the world’s most quake-prone countries, and memories remain vivid of the 2003 Bam earthquake, which killed more than 30,000 people.