Earthquakes

[define: earthquake]
an event in which a buildup of pressure and seismic energy are suddenly released through a failure in ground, which fractures, in the form of vibrations.

[but why?]
two conservative plates, against one and other, abruptly release.

[and where?]
typically at plate boundaries, however not limited to. never above the surface. where it starts it’s called the focus, and the point in line with that on the actual surface is the epicentre.

- The most dangerous factor is the rock type. The looser the rock, the more dangerous.
- Means of measuring: there are several (i.e. Richter scale, measures intensity. It’s a scale of 1-10. However, between 1 and 2, there is a 10x difference.)
- The largest known earthquake - Valdivia, Chile, 1960 @9.5 magnitude.
- How do we know how the locations of these? (seismometer) You need three recording stations to spot the ‘common area’ between them.
- The seismograph is what it produces (the trace with the lines on it.)
- 3 waves: P, S and L.
- In L.A. the earthquake emergency office is on the actual fault lines. (Not very clever!)

[mitigation techniques: earthquakes]

- securing otherwise freestanding items – bookshelves, tables, etc. (BEFORE)
- survival kits (BEFORE/AFTER)
- identify safe locations to go to and create an evacuation plan (wide, open spaces) (BEFORE/AFTER)
- have emergency contacts (BEFORE)
- train all family members, etc. (BEFORE)
- secure water and gas pipes (BEFORE)
- keep contacts and aid lines on hand (BEFORE/AFTER)
- evaluate and choose a safe building location (BEFORE)
- proof buildings (shatterproof glass, shock absorber foundations) (BEFORE)
- for government: network of warning stations (BEFORE) 
- because earthquakes trigger tsunamis, barriers (BEFORE)
- move to high ground in case of tsunami, or go inland (BEFORE) 

[mitigation techniques: volcanoes]

- evacuate away from lava flow (DURING)
- move when earth tremors are sensed (BEFORE)
- lahar sensor (BEFORE)

[we will never have earthquakes/volcanoes forever, as the core can stop releasing heat.]