Earthquake hazards

Hypocentre

Where the earthquakes occur within the crust

Epicenter

The center of the earthquake above ground

Displacement

Rupture and movement of the ground (horizontal and vertical scales in units of Km, displacement scale in units of m)

Seismograph

The recording station

Seismometer

The sensor that moves with the earthquake

Seismogram

The record of an earthquake

What are the two different types of waves emitted by an earthquake

P and S waves

How do you estimate distance of an earthquake

P and S waves have different velocities, so arrival times of each can be used to estimate distance to the earthquake hypocentre

What does the P in P-waves stand for

Primary

What does the S in S-waves stand for

Secondary

Are P or S waves faster

P waves

How do you use the P and S waves to calculate distance

You take the time between S and P wave arrival to determine the distance, the shorter the distance between S and P wave arrival the closer the earthquake

Explain this image

Different S-P times recorded by seismometers in different places (Portland, SLC, and LA) are used to calculate distance of the earthquake and overlaid on top of each other to locate the epicenter of the earthquake

Abbreviation for Richter magnitude

M_L

Abbreviation for Surface wave magnitude

Ms

Abbreviation for Moment magnitude

Mw

Description of Moment Magnitude

Universal measure of magnitude, measured from the size of the earthquake source

Equation for seismic moment

Mo=µLWD (µ = lithology and tectonic regime)

Equation for Moment Magnitude

LogMo=16.05+1.5Mw

Increases in magnitude mean…

Increases in amplitude, duration, frequency content

What would a magnitude 10 earthquake lead to

A rupture around the earth

Earthquake intensity definition

The human-felt scale of earthquake shaking (subective)

What is this called

The Gutenberg-Richter relationship

What is the importance of the Gutenberg-Richter relationship

describes the statistical relationship between the magnitude and frequency of earthquakes, indicating that larger earthquakes occur less frequently than smaller ones.

What are catalogues

Incomplete records of earthquakes (not knowing the completeness of the catalogue can lead to significant errors in interpretation)

What is defined as prehistoric for earthquakes

Pre 1840AD

Liquefaction

Soils become liquid due to shaking causing objects to sink

Paleoliquefaction

Structure in soil where liquefaction occurred allowing you to identify when an earthquake occurred

Steps of hazard analysis

Where are the sources, how many events on each source, metrics of hazard, hazard curve

Definition of Earthquake source

Element of a seismic hazard model that produces earthquakes of a given magnitude range at a given location

Fault sources

Constrain the location, size, and rate of infrequent major earthquakes. Extend the historical record of earthquakes back into prehistoric time

What does an incomplete fault source model mean

Not sure of where all of the faults that could cause earthquakes are

How far can a fault be and still be of interest to a specific area

Less than or equal to 100Km from site