- © 2014 by the Seismological Society of America
We hereby reply to the comments of Noorbakhsh Mirzaei, Elham Shabani, Seyed Hasan Bafrouei (hereafter NES) on our paper published in Seismological Research Letters 84 (2), 233–249 (hereafter Shahvar et al., 2013). We thank the readers for the attention given to the paper, however, we think that its purpose has been considerably misunderstood by them. As clearly mentioned in the Introduction and in the Conclusions, the aim of our paper was to provide a unified earthquake catalog for the Iranian plateau by converting the original magnitudes (Ms, mb, ML, and MN) to a uniform scale (Mw). Our aim was to estimate neither the catalog completeness nor the seismicity parameters.
Our work originated from the lack of a uniform catalog of earthquakes in Iran (both for the fact that data are dispersed among several catalogs and for the fact that they report magnitudes with different scales), which makes research on seismicity and seismic hazard very difficult.
Regarding the comments on the number of zones used to define magnitude conversion relations, it has to be noted (but we think this was already clear from the text) that our subdivision was not based on tectonic arguments but naturally came out from the application of statistics to the data. We started from the six main seismotectonic areas defined by Rham (2009) but found that: (1) the Makran and Kopet–Dagh areas reported too few Mw data to perform any meaningful analysis, and (2) no statistically significant differences between the Alborz and Central Iran zones appeared for any magnitude conversion relation. These two areas could also belong to two different tectonic settings but this is completely irrelevant to our analysis: they show the same conversion relations and it makes no sense to treat them separately to the aim of our paper. The Ockham’s razor principle, on which the scientific method is based, forces us to use—among the many possible models—the one that explains the observations using the lowest amount of parameters. This choice is also supported by the results of the same Mirzaei et al. (1997) who found the same relation by treating the Central Iran and Alborz zones as separate. On the opposite side, the Ms–mb, ML–MN, and Mw–mb relations were found to differ significantly for the Alborz–Central Iran and the Zagros region, which have therefore been treated separately.
About the comments on the depths, the values reported in our paper are the maximum depths described by the different agencies.
For what concerns the choice of the Zagros area, we have followed Alavi (1994, 2004), Agard et al. (2005), Ghasemi and Talbot (2006), and Rham (2009). Alavi (1994, which is one of the most cited papers), states:
The Zagros orogenic belt of Iran is the result of the opening and closure of the Neo‐Tethys oceanic realm, and consists, from northeast to southwest, of three parallel tectonic subdivisions: (1) the Urumieh‐Dokhtar Magmatic Assemblage; (2) the Sanandaj‐Sirjan Zone; and (3) the Zagros Simply Folded Belt.
The NES statement according to which Karimiparidari et al. (2013) established magnitude conversion relations for six separate zones appears to us to be incorrect, because Karimiparidari et al. (2013) computed the conversion relations for whole Iranian plateau, with no segmentation (a subdivision into six areas was used only to calculate the seismicity parameters, not the magnitude conversion relations).
The NES comment on our presumed wrong data entries (“event number 1420 is reported with Mw 5.8 instead of 5.3; or event number 2031 is reported with Mw 4.6 instead of 5.1”) is not correct. The event number 1420 (9 December 1971) is reported as an Mw 5.8 (M0 5.623413×1024) by Earthquake Mechanisms of the Mediterranean Area (EMMA) and Talebian and Jackson (2004). In our catalog the event number 2031 (11 February 1978) is reported with Mw 5.1 (Mo 6.559931×1023 by EMMA, and Jackson and McKenzie, 1984). The event number 7056 (8 November 2011) and the event number 6789 (9 February 2011), are reported under the ID 17525142 and 16852124 in the International Seismological Centre (ISC) catalog. The other events incorrectly reported by National Earthquake Information Center (NEIC) were removed.
Reporting the history of seismic networks (who, when, and why initiated them) was definitely not pertinent to our paper and this information can easily be found in the seismological network manuals for the interested readers.
Regarding the comments on the uncertainty estimation, as described in the section Uncertainty Estimation, the final uncertainties include the contribution to the total error (often unfortunately neglected!) deriving from the original magnitude uncertainties. This makes it clear that magnitude values cannot and should never be written with more than two significant digits (see also Bormann, 2002).
We think that the other comments are not constructive and do not need reply.
For all the above reasons, we feel that the results of our paper are not affected in any way by the comments—appreciated but with which we do not agree—received by NES.