The professor from the Seismology Research Center stated: The occurrence of a small earthquake with a magnitude of 4.0 in Karaj cannot by itself be a definitive indication of the likelihood of a larger earthquake occurring in this region and Tehran.
According to the community service report of Saed News, citing Hamshahri, at 9:00 PM on Saturday, May 3, 2025 (13 Ordibehesht 1404), an earthquake with a magnitude of 4.0 struck the Mahdasht area near Karaj. This event occurred near the epicenter of the December 20, 2017 (29 Azar 1396) earthquake with a magnitude of 5.0 in Malard.
Mehdi Zareh, a professor at the Seismology Research Center, stated in an interview with Mehr News Agency that the 2017 earthquake occurred along the North Tehran fault system, which has the potential to produce earthquakes with magnitudes of 7 or even higher.
However, Zareh emphasized that the occurrence of a small earthquake with a magnitude of 4.0 in Mahdasht cannot by itself be a definitive indication of a larger earthquake in this region.
He added: "It is not possible to definitively conclude that a larger earthquake is imminent from this small single event."
The epicenter of the discussed earthquakes is located near the area of groundwater depletion and land subsidence in the Shahriyar Plain. Prior to and after the 2017 earthquake, several small earthquakes were recorded in this region.
The 2017 earthquake occurred along the Mahdasht fault, south of Karaj, which is part of the western segment of the North Tehran fault system. This fault system is approximately 100 kilometers long and is active, with an estimated recurrence period of earthquakes of about 3,500 years.
Historical evidence suggests that an earthquake in 1177 AD in the east of Bouin Zahra-Eshtehard area was likely caused by activity along this fault system.
Additionally, an ancient earthquake approximately 3,200 years ago is attributed to this fault.
The North Tehran fault has the potential to generate earthquakes with magnitudes of 7 to 7.5, and evidence of large landslides in the area may indicate past severe earthquakes.
Zareh also referred to the September 1, 1962 earthquake in Bouin Zahra, which occurred along the Ipek fault. A segment of this fault, which was active in the 1962 earthquake and likely in 556 AD, is located between eastern Eshtehard, southern Bouin Zahra, and northern Abgarm.
This seismology expert stated: "Segments of the Ipek fault along the border between the mountain and plain in southern Qazvin Plain, southern Bouin Zahra, and the continuation of the southern Eshtehard fault towards the west have been observed."
In the 1962 earthquake, surface ruptures, vertical displacements (uplifting of the southern portion), and left-lateral strike-slip movements were visibly observed. This fault zone extends eastward to the southern Eshtehard fault, the Mahdasht fault south of Karaj, and ultimately to the North Tehran fault.
Zareh noted: "Researchers are currently analyzing data to assess the potential for increased seismic activity in this region."
He added: "For more accurate earthquake predictions, further analyses are needed."
This earthquake has once again drawn attention to the vulnerability of urban areas near active faults, especially in the metropolitan city of Tehran, which is located near the North Tehran fault system.
