Distribution Of Earthquakes Flashcards
the sudden vibration, violent movement of Earth’s surface caused by a rapid release of stored energy
Earthquake
the source from which the energy is released; that is radiating to all directions.
Focus
the point directly above the focus
Epicenter
Distribution of Earthquake Epicenters in the World
Earthquake Belts
About 90% of the world’s earthquakes and 81% of the world’s largest
earthquakes occur along the Ring of Fire.
Circum-Pacific Belt
Distribution of Earthquake Epicenters in the World
Earthquake Belts
the next most seismic region (5-6% of earthquakes and 17% of the world’s largest earthquakes);
It extends from Java to Sumatra through Himalayas, the Mediterranean, and out into the Atlantic.
The belt records earthquakes that are shallow 70 to 300 km from the earth’s surface.
They are mostly intermediate in origin.
Alpide Belt
Distribution of Earthquake Epicenters in the World
Earthquake Belts
the third most prominent earthquake belt.
This earthquake belt runs along the mid-ocean ridges in the Atlantic.
The intensity of most of the earthquakes here is moderate
Mid-Atlantic Ridge
● The principal earthquake epicenter zones are located along the outer margin of the Pacific Oceanbknown as the Circum-Pacific belt or Circum-Pacific Seismic Belt and through the earth’s oceans and along the oceanic ridge system.
● Oceanic ridge is a continuous submarine mountain chain extending approximately 80,000km through all the earth’s ocean.
● Oceanic Ridge System is a continuous underwater mountain range with parts found in every ocean of the world.
● Ocean trenches are deep depressions in the Earth’s crust comprising the deepest part of the ocean.
e.g. Marianas Trench, Tonga Trench, and Philippine Trench
● Mid-ocean ridge is the most extensive chain of mountains on Earth, stretching nearly 65,000 kilometers (40,390 miles) and with more than 90 percent of the mountain range lying in the deep ocean.
Plate Tectonics Theory and Earthquakes
❖ The crust is composed of tectonic plates, and the edges of the plates are called the plate boundaries.
The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults.
Since the edges of the plates are rough, they get stuck while the rest of the plate keeps moving.
Finally, when the plate has moved far enough, the edges unstick on one of the faults and there is an earthquake.
Plate Tectonics Theory and Earthquakes
❖ According to the theory of plate tectonics, Earth is an active planet.
Its surface is composed of many individual plates that move and interact, constantly changing and reshaping Earth’s outer layer.
Volcanoes and earthquakes both result from the movement of tectonic plates.
Plate Tectonics Theory and Earthquakes
❖ Tectonic earthquakes occur at plate tectonic boundaries.
Tectonic plates are constantly moving slowly, but sometimes friction between them causes them lock together and become unable to move.
The waves of released energy move through the Earth’s crust and cause the shaking we feel at an earthquake site.
