The confusion over the magnitude of the earthquake that struck Bhuj yesterday remains as the media had reported two figures. So what exactly is the correct magnitude.
Earthquakes produce three different types of seismic waves.
The third one is the Surface wave. Magnitude based on the S-wave according to the IMD is 7.6, comparable to the U.S. Geological Survey's estimate 7.9. Maximum damage in any earthquake is primarily caused by the S- wave, also called shear wave due to its shearing action. S-wave causes elastic up and down vibrations perpendicular to its direction of travel. The P-wave, on the other hand causes a train of compressions and dilatations parallel to the direction of propagation.