2 Sept 2009 15:00:
7.3 on the Richter scale Earthquake in Lat/Lon S8.223 LS E107.449, depth: 30 kilometer below sea level, about 142 kilometer southwest Tasikmalaya, West Java Indonesia.

An earthquake (also known as a tremor or temblor) is the result of a sudden release of energy in the Earth’s crust that creates seismic waves. Earthquakes are recorded with a seismometer, also known as a seismograph. The moment magnitude of an earthquake is conventionally reported, or the related and mostly obsolete Richter magnitude, with magnitude 3 or lower earthquakes being mostly imperceptible and magnitude 7 causing serious damage over large areas. Intensity of shaking is measured on the modified Mercalli scale (http://en.wikipedia.org/wiki/Earthquake).

Earthquakes can be recorded by seismometers up to great distances, because seismic waves travel through the whole Earth’s interior. The absolute magnitude of a quake is conventionally reported by numbers on the Moment magnitude scale (formerly Richter scale, magnitude 7 causing serious damage over large areas), whereas the felt magnitude is reported using the modified Mercalli scale (intensity II-XII).

Richter magnitude scale
The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). The original formula is:[4]
ML = log10A − log10A0(delta),

(Based on U.S. Geological Survey documents. http://earthquake.usgs.gov/learning/faq.php?categoryID=2)

Mercalli intensity scale

The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. The scale quantifies the effects of an earthquake on the Earth’s surface, humans, objects of nature, and man-made structures on a scale of I through XII, with I denoting not felt, and XII one that causes almost complete destruction. The values will differ based on the distance to the earthquake, with the highest intensities being around the epicentral area. Data are gathered from individuals who have experienced the quake, and an intensity value will be given to their location.

The Mercalli scale originated with the widely used simple ten-degree Rossi-Forel scale, which was revised by Italian vulcanologist Giuseppe Mercalli in 1883 and 1902. The terms [copy missing] or Mercalli scale should not be used unless one really means the original ten-degree scale of 1902.
In 1902 the ten-degree Mercalli scale was expanded to twelve degrees by Italian physicist Adolfo Cancani. It was later completely re-written by the German geophysicist August Heinrich Sieberg and became known as the Mercalli-Cancani-Sieberg (MCS) scale. The Mercalli-Cancani-Sieberg scale was later modified and published in English by Harry O. Wood and Frank Neumann in 1931 as the Mercalli-Wood-Neumann (MWN) scale. It was later improved by Charles Richter, the father of the Richter magnitude scale. The scale is known today as the Modified Mercalli Scale and commonly abbreviated MM.

The lower degrees of the MM scale generally deal with the manner in which the earthquake is felt by people. The higher numbers of the scale are based on observed structural damage. The table below is a rough guide to the degrees of the Modified Mercalli Scale. The colors and descriptive names shown here differ from those used on certain shake maps in other articles.