Three small earthquakes in the east and northeast of Tehran; Are these events just normal earth tremors or should they be considered a warning of a greater danger?
The recording of three small earthquakes in the east and northeast of Tehran on November 23 and 24 has once again drawn attention to the activity of active faults in this region.
These earthquakes occurred in the vicinity of Sorkhehsar and Lavasan; An area that is considered one of the seismic zones of Central Alborz due to the presence of important fault systems such as Mesha fault and North Tehran fault. But can the repetition of small earthquakes be a sign of a large earthquake?
In order to investigate the origin of these events, the geological features of the region and the level of seismic risk, we have had a conversation with Mehdi Zare, a geologist and seismologist. You can read the text of this conversation below:
* On the 23rd and 24th of Aban, three small earthquakes with magnitudes of 2.8, 2.6 and 3 on the Richter scale were recorded in the east and northeast of Tehran, around Sarkhehsar and Lavasan. What is the origin of these earthquakes?
The origin of these three small earthquakes is the activity of the seismic zone of the Sorkhehasar fault and the North Tehran fault. The area of ​​Lavasan, Pardis, Bomhen, Rodhen and around Damavand is one of the most active seismic zones around Tehran.
The Mesha fault is a strike-slip system with a length of more than 200 km. This fault and the eastern terminus of the North Tehran fault meet near Kalan village in Lavasanat and create an important zone in terms of tectonic collision and interaction. For this reason, the density of microearthquakes and seismic clusters is high in this area.
In recent years, numerous small and medium earthquakes have been recorded in this area; Especially since the beginning of this year, there have been several events with a magnitude of more than 3 and even more than 4 Richter. These events indicate the gradual release of stress and the deformation rate of the earth’s crust in Central Alborz.
The reported coordinates and depth of these earthquakes, which are reported to be about 8 km, are also consistent with the activity pattern of this fault system.
* Can the occurrence of these small earthquakes mean that they are pre-earthquakes and the possibility of a large earthquake in Tehran?
From a scientific point of view, the occurrence of small earthquakes alone is not a sign that a major event is imminent. In many cases, these earthquakes are part of the normal seismic activity of the region or a phenomenon called a seismic swarm (Swarm), during which several earthquakes with limited magnitudes occur in a range and at a relatively close time interval and release limited energy.
However, one should not neglect the high seismicity potential of this area, the Mesha fault has the ability to create an earthquake with a magnitude of more than 7. The historical earthquake around 1830 AD, with an approximate magnitude of 7, is also related to this fault or its intersection with other geological structures.
Is Tehran waiting for a big earthquake? Three microquakes and one alarming fault
The long time interval since the last major event, the possibility of stress accumulation in active faults and the continuation of recent seismic activities increase the necessity of continuous monitoring of this area. Therefore, although it is not possible to conclude the imminent occurrence of a large earthquake from these small earthquakes, preparation against earthquakes and avoiding the increase of population loading in this area should be taken seriously.
The repetition of small earthquakes in the east and northeast of Tehran, alone is not an alarm for the imminent occurrence of a large earthquake; But the geological position of this region and the presence of active faults such as Masha and North of Tehran remind us of the necessity of serious attention to the seismic risk.
Experts emphasize that it is not possible to predict the exact time of an earthquake by relying on microearthquakes, and the main solution is to reduce damage, scientifically monitor faults, comply with construction standards, manage urban development, and increase public preparedness against earthquakes.
What can be understood from the repetition of small earthquakes in the east and northeast of Tehran is the need to pay more serious attention to the seismic situation of this region. An area that is always at risk of earthquakes due to its proximity to active faults, including Mesha fault and North Tehran fault.
Although the occurrence of several micro-earthquakes in a short period of time does not mean that a large earthquake is near, and currently it is not possible to predict the exact time or place of such an event, but this issue should not lead to ignoring the seismic risk.
* What is your advice in this regard?
Tehran and its surrounding cities have faced the expansion of construction and population growth in the past decades; An issue that can increase the extent of damage in the event of a severe earthquake.
Therefore, it is very important to pay attention to the quality of construction, retrofitting vulnerable buildings, respecting the privacy of faults and preparing critical infrastructures, and it is also necessary to continuously review seismic data and make its results available to people in clear language.
Earthquake risk cannot be managed by predicting its occurrence time; But it is possible to significantly reduce its human and economic cost by preparing, planning and reducing vulnerability.
