The 2013 Saravan earthquake occurred with a moment magnitude of 7.7 at 15:14 pm IRDT (UTC+4:30) on 16 April. The shock struck a mountainous area between the cities of Saravan and Khash in Sistan and Baluchestan Province, Iran, close to the border with Pakistan, with a duration of about 25 seconds. The earthquake occurred at an intermediate depth in the Arabian plate lithosphere, near the boundary between the subducting Arabian Plate and the overriding Eurasian Plate at a depth of about 80 km.It was the largest earthquake in Iran within the last 300 years, equal in magnitude to the one that shook East Azerbaijan in 1721, killing up to 250,000 people, and possibly the largest in the last half-century. The earthquake followed a magnitude 6.3 event near Bushehr. The town of Mashkel was close to the quake's epicentre, and around 85 percent of the city's buildings were demolished. Thirty-five people were killed in the earthquake.

The moment magnitude scale (MMS; denoted explicitly with Mw  or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude scale (ML ) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales.

Moment magnitude (Mw ) is considered the authoritative magnitude scale for ranking earthquakes by size. It is more directly related to the energy of an earthquake than other scales, and does not saturate—that is, it does not underestimate magnitudes as other scales do in certain conditions. It has become the standard scale used by seismological authorities like the U.S. Geological Survey for reporting large earthquakes (typically M > 4), replacing the local magnitude (ML ) and surface wave magnitude (Ms ) scales. Subtypes of the moment magnitude scale (Mww , etc.) reflect different ways of estimating the seismic moment.