EQ Flashcards
Most earthquake damage comes from
Ground shaking
Earthquake movement generates this which propagates through earth
Seismic waves
Verisk uses this to describe the interaction between buildings, including both structural and non structural components as well as their contents, and the local intensity to which they are exposed
Damage functions / Damageability relationships
Sheer stress applied across fault
Elastic deformation
90% of earthquake occurs along
Plate boundaries
Describes the movement of the mantle
Mantle convection
Most likely magnitude of an event to occur on each fault
Characteristic magnitude
Western US data on more than 200 faults includes slip rate , length and width of fault, dip angle, characteristic magnitude and frequency of event
USGS data
Verisk uses this to classify the earthquake magnitude
Movement magnitude
Best indicates the destructive power of an earthquake
Energy release
Small magnitude and produce shorter periods of waves
Crustal earthquake
Larger magnitude and produce longer periods of waves
Subduction earthquakes
Largest increase in velocity recorded by a particular station during earthquake. What is experienced by a particle on earth
Peak ground acceleration PGA
What is experienced by a building
Spectral acceleration SA
Earthquake related perils
Ground shaking,
Tsunami,
Landslide,
Liquefaction,
Fire following,
Sprinkler leakage
Tsunamis can be generated by
Earthquake
Landslides
Meteorites
Volcanic Eruptions
Capable of generating tsunami
Tsunamigenic
Destruction from tsunamis is the direct result of
Inundation
Wave impact on structures
Erosion
Location data needed for earthquake
Epicentre
Focal depth
Fault or seismic zone
Faults tend to produce earthquakes of a certain magnitude at fairly regular intervals
Characteristic of fault segment
Verisk models time independent catalog for all regions except for which are time dependent catalog
Cascadia subduction zone
Characteristic California earthquakes
How is stress accumulation across a region measured to determine plate motion velocities
GPS data
Empirical relationship between the frequency and magnitude of earthquakes - cumulative annual frequency of earthquakes decreases as magnitude increases
Gutenberg Ritcher magnitude rate distribution
What controls the magnitude of background seismicity
G R curve
Shows the difference between soil and rock types
Seismic site amplification
History of how displacement, velocity and acceleration vary with time.
Time histories
What time history do we focus on
Acceleration time history
Recorded acceleration vs time
Ground motion
To see which frequencies of oscillation are more prevalent during an earthquake by allowing to break the acceleration time history in all the different frequencies and understand their Amplitude ( amplitude as a function of frequency)
Fourier spectrum
Tall structures responds to ____ period of shaking
Long
____ structures respond to short period of shaking
Short
Frequency with which the building wants to vibrate
Natural frequency
When we subject building to a ground motion with a frequency that is very similar to its natural frequency, the amplitude of vibration increases. This phenomenon is called ___
Resonance
If a building experiences mechanical resonance, the deformation can be ____
Large enough to produce severe damamge
What influences the natural period of vibration of structures?
- Stiffness
- Quantity and distribution of mass
As stiffness and fixity increases natural period of building ____
Decreases
Less slender a building is, the ____ will be its natural period
Lower
A building with lower mass will have ____ period of vibration
Lower
Very simple structure where the mass M is concentrated at a point connected to the ground with a column of stiffness K - used to identify the natural period of vibration
SDOF Single degree of freedom oscillator
Stiffer the structure ___ the natural period of vibration
Shorter
Skyscrapers are heavy and very flexible and hence their natural period is
High
As mass increases and stiffness decreases, the natural period
Increases
Low rise buildings are light and stiff and hence their natural frequency is
Low
If mass decreases and stiffness increases , the natural period
Decreases
Mass depends on
Material and dimension
Stiffness depends on
Material, dimensions and structural system
Building vulnerability depends mainly on
Material
Resisting mechanism
Height
In order to estimate damage and loss, mathematical relationships are employed correlating ground motion intensity to building structure damage. these relationships are referred to as
Damage function
Loss divided by replacement value
Mean damage ratio
How do we compute Spectral Acceleration
Single degree of freedom oscillator SDOF
