Majid Farahani, a member of the Tehran City Council, says that if there is an earthquake in the capital, one and a half million people will be at risk of perishing, and as such Tehran is not a good place to live. A new study has shown that there may be severe earthquakes in Tehran between the next six and twelve years.
Scientific evidence published in the past few years shows that the likelihood of a major earthquake in Tehran is very high, and experts have repeatedly warned of this. One of these pieces of evidence is the state of the north Tehran fault. This fault tends to erupt every 3000 to 3500 years in Tehran, and that period has already arrived.
On the other hand, the study of the seismic status of the Tehran region also points to the possibility of an earthquake. Mehdi Zareh, professor of seismology, explains: “The last major seismic event that took place in Tehran dates back to 1830, when a strong earthquake hit within the 100 km radius of Tehran. If we look at this statistically, every 200 years earthquakes of around 7-richter magnitude shake the area; and now it has been 189 years since the last time. Of course, it does not mean that exactly every 200 years ago such an earthquake should strike Tehran.”
But the new study by the researcher of the Seismological Research Institute shows that the situation is now in a much more dangerous state than the past, and that the possibility of a severe earthquake in Tehran is high. In this study, the probability of occurrence of an earthquake occurring in areas around Tehran at a radius of 100 km from the city center was investigated for a period of 6-12 years.
Zareh’s new study shows that this area has a high potential for a severe earthquake. A similar situation exists for the populous cities of Karaj, Tabriz, Mashhad and Qom as well. All of these areas are in a seismic state in terms of the coefficient of variation of seismic parameters of Iran over the last 42 years. Data analysis for the first 32 years of the same period (1976-2008) showed that all of the areas where earthquakes occurred at the time (2008-2019) with magnitudes of more than 6 were relatively high in the zones with the least changes in the coefficients observed, and in the period of 6 to 12 years, the areas around populated cities are high on the probability of a severe earthquake.
Mehdi Zareh pointed out that the results of this study are in the realm of probability and that there is no definite answer to the time of the earthquake in Tehran and other populous cities. He added that “The mid-term forecast of this study, which describes the state of the earthquake incidence in a 6-year period, shows that there is the probability of a relatively significant earthquake in the region around Tehran in a window between the next 6 and 12 years. Our estimate is, that significant probability of occurrence is between 40% and 70%. It does not mean that such an incident will surely occur in this period. It may not even happen in the next 50 years. However, our calculations give us such a possibility.”
But the results of this study show that other areas are in danger in addition to Tehran. In this study the seismic coefficient of different regions of Iran between 1976 and 2008 was investigated. It was concluded that in the last 10 years the most severe earthquakes occurred in the areas with the lowest seismicity. But in these areas where the seismic coefficient was low, only part of the area was hit with severe earthquakes during recent years, while some other areas remained unaffected. This was the subject that brought about some predictions about the future earthquakes in some parts of Iran.
Zareh explained: “In order to predict the long-term and mid-term probability of the earthquake, we examined the coefficient of seismic changes between 1976 and 2008 in different regions of Iran, and concluded that over the past 10 years the most severe earthquakes occurred where the seismic coefficient was at lowest until 2008. This creates an interpretation for us from which we can obtain the images of the areas where the risk of an earthquake is higher in the future. In other words, we can look at the risk of a high magnitude earthquake (6 Richters) earthquake in different parts of the country from now to six years into the future.”
Zareh concluded: “Of course, the number of these areas is high, but we can focus more on areas with a significant population. In general, for the six years ahead of us, more attention should be paid to areas such as Karaj, Tehran, Tabriz, and east of Alborz as well as the eastern parts of Mazandaran.”