Lecture 2- Earthquake Lcoation And Magnitude Flashcards
How is the hypocentre of an earthquake found (three coordinates)
- Latitude
- Longitude
- Focal depth
What are the primary effects of earthquakes?
The permanent displacement of blocks either side of the fault (fertile or horizontal)
What are secondary effects of earthquakes?
-ground shaking, liquefaction, building damage, etc
What percentage of earthquakes occur at plate margins?
> 95%
What is the typical depth of earthquakes at constructive and conservative plate margins?
0-15 km (shallow)
What is the range of focal depth at convergent plate margins?
0-700 km (benioff zone)
Why is frequency forecasting difficult for intra -plate earthquakes?
They have long reoccurrence intervals and are randomly distributed
What does a seismograph measure?
Ground displacement, velocity or acceleration vs time
What is a seismograph?
The output of a seismograph
To what degree of accuracy can modern seismographs detect shaking?
10^-10 m
How many different seismographs exist at one station?
6
What are the six different seismographs located at a singular station?
- sensitive verticals
- strong motion vertical
- N/s sentisitve
- n/s strong motion
- e/w sensitive
- e/strong vertical
The time interval between what aids in epicentre location?
P and S waves
What causes an increase in the time interval between p and S waves?
Distance from the epicentre (of the seismograph station)
What allows for absolute identification of epicentre location?
The overlap between three different seismograph stations
