(Public domain.) The time, location, and magnitude of an earthquake can be determined from the data recorded by seismometer. Seismometers record the vibrations from earthquakes that travel through the Earth. Each seismometer records the shaking of the ground directly beneath it.

Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future. USGS scientists can only calculate the probability that a significant earthquake will occur in a specific area within a certain number of years.

The distance between the beginning of the first P wave and the first S wave tells you how many seconds the waves are apart. This number will be used to tell you how far your seismograph is from the epicenter of the earthquake.

Scientists use triangulation to find the epicenter of an earthquake. When seismic data is collected from at least three different locations, it can be used to determine the epicenter by where it intersects. Every earthquake is recorded on numerous seismographs located in different directions.

Where do earthquakes occur?

• The world’s greatest earthquake belt, the circum-Pacific seismic belt, is found along the rim of the Pacific Ocean, where about 81 percent of our planet’s largest earthquakes occur.
• The Alpide earthquake belt extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic.

By magnitude

Here are the 10 Safest Cities in California for 2021

• Danville.
• Rancho Santa Margarita.
• Moorpark.
• Rancho Palos Verdes.
• Aliso Viejo.
• Lake Forest.
• Yorba Linda.
• Laguna Niguel.

​​California’s Largest Recorded Earthquakes Since 1800, Ranked by Magnitude​

A magnitude 7.1 earthquake struck southern California on July 5, 2019 at 8:20 p.m. local time (July 6 at 03:20 UTC). This event was centered near the July 4, 2019 magnitude 6.4 earthquake. Map shows past earthquakes and the epicenter of the magnitude 7.1 July 5, 2019 southern California earthquake (USGS Public domain).

Scientists have pinpointed a long-overlooked portion of the southern San Andreas fault that they say could pose the most significant earthquake risk for the Greater Los Angeles area — and it’s about 80 years overdue for release. But there could be a silver lining.

For which country do we locate the most earthquakes? Japan. The whole country is in a very active seismic area, and they have the densest seismic network in the world, so they are able to record many earthquakes.

Normally, earthquakes below magnitude 3 or so are rarely felt. However, smaller quakes from magnitude 2.0 can be felt by people if the quake is shallow (few kilometers only) and if people are very close to its epicenter and not disturbed by ambient factors such as noise, wind, vibrations of engines, traffic etc.

magnitude 3 earthquake

A small earthquake far away will probably not be felt at all, but if you do feel it, it will be a subtle gentle shake or two that is easier to feel if you’re still and sitting down.