A macroseismic twelve-degree intensity scale (I to XII) published by Wood and Neumann (1931) (abbreviated MM). It is based on the translation into English by Wood and Neumann (1931) of the macroseismic scale published by Sieberg (1923), which in its later version (Sieberg, 1932) became widely known as the Mercalli-Cancani-Sieberg scale. Therefore, the name Modified Mercalli scale is inappropriately chosen. Even more, after Richter (1958) overhauled the Wood and Neumann version completely, thus becoming the Modified Mercalli Scale of 1956 (MM56), which is only very remotely linked to Mercalli. Reference to the MM scale is further complicated by recent modifications introduced by Stover and Coffman (1993) to the 1931 version of the MM in conjunction with the revision of the seismicity of the United States between 1568 and 1989. This latest upgrade is now referred to as MMI. The MM scale is widely used, not only in the USA (although MMI has become there now most popular because of the Did you feel it? system maintained by the USGS) but also in many countries in and outside of North America. For details see Chapter 12 of this Manual, Musson et al. (2010) and Atkinson and Wald (2007)