Convergent plate boundaries
- A smaller earthquake following the main shock of a large earthquake. The Tohoku Earthquake of 2011 had over 11000 aftershocks.
- Also known as a destructive plate boundary, this is where two tectonic plates move towards each other and collide. One plate is forced underneath the other being destroyed in the process.
Deep focus earthquakes
- The outermost, solid layer of the earth.
- Occur at a depth of 300-700 km underground. Only discovered in 1931, they are still only partially understood.
- A natural hazard becomes a disaster when there is significant damage to property and/or loss of life.
- A sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth’s crust.
- The point on the earth’s surface vertically above the focus of an earthquake.
- A fracture in a rock formation along which there has been movement of the rocks on either side of the fracture.
- The line on a rock surface or the ground that traces a geological fault.
- The place of origin of an earthquake or moonquake.
- A mild tremor preceding the violent shaking movement of an earthquake.
- A danger or risk.
- Most earthquakes are interpolate earthquakes. That is to say that they occur at the boundary between two earthquakes.
- Intraplate earthquakes are rare and occur far from plate boundaries but along faults in the normally stable interior of plates.
- A collapse of a mass of earth or rock from a mountain or a cliff.
- Is a phenomenon where the shaking of the earth by an earthquake reduces the strength and stiffness of the soil and forces the liquid in the soil to rise to the surface.
- The size of an earthquake as measured by the energy released.
- A megathrust earthquake is a very large earthquake that occurs in a subduction zone where one plate is forced under another.
- A twelve point scale for expressing the local intensity of an earthquake ranging from I (virtually imperceptible) to XII (total destruction)
Liquefaction in Christchurch, NZ, 2011.
Liquefaction in Tokyo, Japan, 2011.
Ring of fire
Seismic waves explanation.
- A natural hazard is an extreme event that occurs naturally and causes damage to property and loss if life.
- The earth’s crust is cracked into different pieces called tectonic plates. Earthquakes can often be found at the plate boundaries.
- Where two tectonic plates meet.
- A way of measuring earthquakes. It is a logarithmic scale so that a difference of one has a roughly thirty fold difference in size.
- The zone of activity surrounding the Pacific Ocean and the Pacific plate.
- Is the modification of existing buildings so that they are more resistant to earthquakes.
- The waves of energy that travel out from an earthquake and are measured my seismographs.
Shallow focus earthquakes
Zones of activity
- Also called a seismometer. An instrument designed to measure earthquakes. It measures their duration and size.
- An earthquake that occurs between 0-70 km underground.
- A tiltmeter is an instrument designed to measure very small changes from the vertical level. Used extensively around volcanoes, scientists use their readings to try to predict when an eruption might be imminent.
- A long high sea wave caused by an earthquake or other event.
- Areas, usually along plate boundaries, where earthquakes and volcanoes are common.