How to measure the strength of the FM radio signal

How to Measure Earthquake Strengths

The strength of earthquakes is measured with seismographs. The devices record the strength of ground movements, the so-called magnitude. Around 100,000 magnitude 3 earthquakes occur around the world every year. Around 1600 have the strengths 5 or 6. A major quake has at least the value 8 and occurs about once a year. The strongest earthquake recorded to date had a magnitude of 9.5 and occurred in Chile in 1960.

Earthquakes can have different effects in the region, depending on their duration, soil conditions and construction methods. Usually the following applies:

- Strength 1-2: weak tremor, only to be detected by instruments

- 3: Felt only near the epicenter

- 4-5: 30 kilometers around the center noticeable, slight damage

- 6: Dead and severe damage in densely populated regions

- 7: Houses collapse in large areas, many dead

- 8: Devastation within hundreds of kilometers, very many dead

The intensity of the quake does not increase evenly upwards. Rather, the shock energy increases by over 30 times with each strength-point difference. A magnitude 6 quake releases around 1000 times as much energy as a magnitude 4 quake. The energy of such a magnitude 6 quake roughly corresponds to that of the atomic bomb explosion over Hiroshima.

Richter scale is now considered out of date

In the past, the magnitude of the earthquake was determined according to the so-called Richter scale. The American geophysicist Charles Francis Richter had developed the scale in 1935 especially for California, where tremors occur more frequently along the St. Andrew's Trench. However, the classic Richter scale is not particularly accurate in the case of large earthquakes. Earthquake researchers therefore use more modern magnitude scales today.

The cause of the earthquake is a sudden release of tensions, which can result from the friction of earth plates against each other or from one plate submerging under another.