Earthquakes

Trembling or shaking his head movement Earth's surface. Most earthquakes are minor tremors.Usually the larger the earthquake began to shake slightly, but in the rapid formation of one or more violent shocks, and, ultimately, the gradual reduction of forces in the vibration, known as aftershocks. Point of origin of the earthquake ground floor is your concern, this focus on the surface of the top of the epicenter. The magnitude and intensity of the earthquake is by the use of scale, for example, the Richter scale and Mercalli scale.

Causes of Earthquakes

Most of the earthquake is the cause and effect relationship between compression or traction forces to create a large-scale movement of lithosphere plates constitute the edge of the Earth's surface. The immediate cause of the sudden release of pressure on a deeper earthquakes along faults or fracture in the Earth's crust caused by the movement of blocks of rocks against each other. These movements caused by vibration and around the Earth through a wave, because the waves produced when a pebble dropped in the water. Volcanic eruptions, landslides, landslides, and causing an explosion, but also an earthquake, but most of them in the local scope only.

Seismic

There are several types of seismic waves, including P, or primary waves, which is extruded and travel faster, and S, or secondary wave, which is horizontal, ie perpendicular to the direction of movement of the Earth's vibration. Is divided into several main types of surface waves, known as the L or long-term waves. As the rate of P and S waves change the density and hardness of the material, cross-border land between the region known as the crust, mantle and the Earth's core have been aware of scientists who deal with seismic analysis and interpretation of seismic waves, seismographs are used to record P, S, L and wave. The disappearance of S waves at depths of 1,800 miles (2,900 km) indicates that at least some outside the Earth's core is liquid.

The earthquake damage

The impact of the strongest earthquake in a wide range of areas near the epicenter. Soil surface crack and the failure to reach the surface often occurs, the horizontal and vertical displacement of a few meters generally. The campaign did not appear in the earthquake, the light cycle, campaign, called fault creep can be accompanied by microearthquakes too small to feel. Extent of earthquake vibration and subsequent damage to an area depends partly on the terrain. For example, seismic vibration, longer life and greater volatility on the surface of loose material, such as poor compacted fill or river deposits, a small mountain fruit. The most serious damage occurred in densely populated urban areas, rather than building structures to withstand strong vibration. Have reported that waves can produce vibrations, building damage, and to break the water and natural gas pipeline started uncontrollable fires.

The destruction and loss of life caused by the earthquake continued to decline in the structure, glass and objects. Flexible architecture built on the bedrock is usually more resistant to earthquake damage of the rigid structure, the establishment of loose soil. In some areas, the earthquake could trigger landslides sliding down hillsides, can be buried below the house. A submarine earthquake waves caused by the devastating tsunami waves outward epicenter of the quake and flooding coastal cities.

Earthquake
On average, the 1000 earthquake intensity of 5.0 or higher, an annual record. A major earthquake (intensity 8.0 or higher) occur each year a major earthquake (intensity 7,0-7,9) occurs 18 times a year a strong earthquake (intensity 6.0-6.9) 10 months, moderate earthquakes (intensity 5.0-5.9 more), twice a day. Since most of which occurred in the ocean or sparsely populated areas, all have been ignored, but the earthquake. The most important earthquake in Lisbon, Portugal (1755), New Madrid, Missouri (1811 and 1812), Charleston (1886), Assam, India (1897 and 1950), San Francisco ( 1906), Messina, Italy (1908), Gansu, China (1920), Tokyo, Japan (1923), Chile (1960), Iran (1962), Managua, Nicaragua (1972),Guatemala (1976), Hebei, China (1976), Mexico (1985), Armenia (1988), Luzon, Philippines (1990), ñ, Japan (1993), Kobe, Japan (1995), Turkey Yizi Mi Special (1999), Central Region (1999), Oaxaca, Mexico (1999). Lisbon and Chilean earthquakes accompanied bytsunamis. In the Ching Ming Festival in 1964, an earthquake in North America, the most serious attack in Alaska, measuring from 8.4 8.6 intensity. Apart from raising the 70,000 square miles (181.3 thousand square kilometers) of land and devastating several cities, triggering tsunami, caused by damage to Southern California.

10 of the 15 largest earthquakes in the United States occurred in Alaska, and eight of the 15 largest continental United States occurred in California. The recent earthquake, the U.S., including in February 1971, the campaign's San Fernando fault near Los Angeles. It has shaken the area for 10 seconds, to promote some mountains 8 feet (2.4 meters) increase, the losses caused by the death 64 people worth 500 million U.S. dollars. In 1989, Loma Prieta earthquake, the Santa Cruz to shake hands for 15 seconds, the intensity of 7.1, killing 67 people, collapsed buildings and bridges. In January 1994, a 6.6 earthquake, its epicenter in N Los Angeles, causing significant damage to urban infrastructure, thousands of people homeless.