The Mercalli scale is a seismic scale used to measure the intensity of an earthquake. The measurement is based on observations and experiences, and it is currently measured on a scale of 12 degrees of intensity, indicated by Roman numerals I through XII.
The original Mercalli scale was formulated in the late 1800s and early 1900s as a 10-degree scale. It was later modified several times, and its current form is known as the Modified Mercalli scale. The lower end of the scale is based on reports from people regarding the intensity of the effects they experienced, and the data is collected to form maps of intensity. The upper levels are generally based on observations of destruction caused by an earthquake, such as structural damage. The Mercalli scale differs from the Richter scale, which measures the magnitude of earthquakes.Learn More
California has a relatively high number of earthquakes due to its position on both the Pacific and North American Plates. These plates are in constant motion, and earthquakes occur when their sides slip against one another suddenly.Full Answer >
A diagram that uses the Richter scale is used to measure the magnitude of an earthquake. When an earthquake takes place, a device called a seismograph records the earthquake's vibration, and multiple seismographs can form a coherent picture. From the resulting diagram, the earthquake's force can be determined.Full Answer >
An earthquake is defined as a series of vibrations within the earth's crust that are caused by the rupture of its rocks. This rupture is due to the gradual accumulation of elastic strain within the crust.Full Answer >
The Chilean earthquake of May 22, 1960, known also as the 1960 Valdivia earthquake or Great Chilean earthquake, lasted about 10 minutes. However, it was preceded by a foreshock sequence that began on May 21. The aftershocks that followed lasted until Nov. 1 of that year. This nearly six-month-long seismic event resulted in approximately 10 earthquakes measuring greater than 7.0 magnitude.Full Answer >