Early casualty estimates and medical help management after the M7.3 Kermanshah earthquake of November 12, 2017 in Iran.

Medical responses to fatal earthquakes have to be rapid to save lives. Here we report the QLARM alert that was issued less than an hour after the magnitude 7.3 Kermanshah, Iran, earthquake of 2017 and the following medical response. The near-real-time estimates of fatalities were 520, on average, and it took official and news reports about 2 days to settle on a minimum of 630 fatalities as a final count. The response of various Iranian agencies was rapid and effective, facilitated by the relatively small area of the disaster (radius of about 50 km). Although this disaster was not large enough to require international first responders to rush to the scene, it is clear that in very large earthquake disasters, a fast, accurately informed response saves lives. For international teams to be of optimal use, the locations and functionality levels of health facilities should be known. This information could be included in the earthquake alerts, but the necessary worldwide data on hospitals are currently not available.

Variations in earthquake-size distribution across different stress regimes.

The earthquake size distribution follows, in most instances, a power law, with the slope of this power law, the 'b value', commonly used to describe the relative occurrence of large and small events (a high b value indicates a larger proportion of small earthquakes, and vice versa). Statistically significant variations of b values have been measured in laboratory experiments, mines and various tectonic regimes such as subducting slabs, near magma chambers, along fault zones and in aftershock zones. However, it has remained uncertain whether these differences are due to differing stress regimes, as it was questionable that samples in small volumes (such as in laboratory specimens, mines and the shallow Earth's crust) are representative of earthquakes in general. Given the lack of physical understanding of these differences, the observation that b values approach the constant 1 if large volumes are sampled was interpreted to indicate that b = 1 is a universal constant for earthquakes in general. Here we show that the b value varies systematically for different styles of faulting. We find that normal faulting events have the highest b values, thrust events the lowest and strike-slip events intermediate values. Given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress.