<p>Statements such as:</p>
<blockquote>
<p>Historical data suggest there is a major earthquake in Tehran every 158 years</p>
</blockquote>
<p>should not be interpreted as a number without variation. It is an average number of years. What the statement doesn't state is the error range for the 158 year time period.</p>
<p>Additionally, such a statement is a very general statement. The statement doesn't state which locations in Iran this applies to, or which fault or faults it applies to. One cannot draw to many conclusions from it.</p>

CC BY-SA 4.0
2023-07-19T05:35:05.253Z
2023-07-19T05:35:05.253Z
Fred
<p>In <a href="https://reliefweb.int/report/iran-islamic-republic/iran-national-disaster-meeting-be-held-tehran" rel="nofollow noreferrer">this</a> site (published on 6 November 2001) I found the following information:</p>
<blockquote>
<p>Historical data suggest there is a major earthquake in Tehran every 158 years and the last one there was in 1830.</p>
</blockquote>
<p>The <a href="https://en.m.wikipedia.org/wiki/1990_Manjil%E2%80%93Rudbar_earthquake" rel="nofollow noreferrer">1990 Manjil-Rudbar earthquake</a> occured 160 years after the last major earthquake in Tehran, just 2 years after reaching the 158 years interval.</p>
<p>Can we say the 1990 earthquake postponed a major earthquake in Tehran for another century?</p>
<p>It's true that the fault that caused the 1990 earthquake differs from the fault that caused the 1830 one; but the epicenters are close in a geographical sense and the seismic energy of the Earth got evacuated well in the region after the 1990 earthquake.</p>
<p>There was alao a 5.2 magnitude earthquake near Tehran on <a href="https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_Iran" rel="nofollow noreferrer">2017-12-20</a>; but that can't be counted a major earthquake. The 1830 earthquake had a magnitude of 7.1.</p>
<p>P.S. I don't know if evacuated is a good word here.</p>

<geology><geophysics><earthquakes><seismology>
Did the 1990 Manjil-Rudbar earthquake postpone a massive earthquake in Tehran?
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# Did the 1990 Manjil-Rudbar earthquake postpone a massive earthquake in Tehran?

(Asked by: username_0 on 2023-07-19)

In [this](https://reliefweb.int/report/iran-islamic-republic/iran-national-disaster-meeting-be-held-tehran) site (published on 6 November 2001) I found the following information:

> Historical data suggest there is a major earthquake in Tehran every 158 years and the last one there was in 1830.

The [1990 Manjil-Rudbar earthquake](https://en.m.wikipedia.org/wiki/1990_Manjil%E2%80%93Rudbar_earthquake) occured 160 years after the last major earthquake in Tehran, just 2 years after reaching the 158 years interval.

Can we say the 1990 earthquake postponed a major earthquake in Tehran for another century?

It's true that the fault that caused the 1990 earthquake differs from the fault that caused the 1830 one; but the epicenters are close in a geographical sense and the seismic energy of the Earth got evacuated well in the region after the 1990 earthquake.

There was alao a 5.2 magnitude earthquake near Tehran on [2017-12-20](https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_Iran); but that can't be counted a major earthquake. The 1830 earthquake had a magnitude of 7.1.

P.S. I don't know if evacuated is a good word here.

**Tags:** geology, geophysics, earthquakes, seismology


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## 1 answers

### Answer by username_1 on 2023-07-19. Score: 2 | Accepted answer

Statements such as:

> Historical data suggest there is a major earthquake in Tehran every 158 years

should not be interpreted as a number without variation. It is an average number of years. What the statement doesn't state is the error range for the 158 year time period.

Additionally, such a statement is a very general statement. The statement doesn't state which locations in Iran this applies to, or which fault or faults it applies to. One cannot draw to many conclusions from it.


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