Chapter 2 - Earthquake Characteristics Flashcards
What is PGA?
PGA = peak ground acceleration. max recorded ground acceleration of an earthquake at a particular site
What is magnitude?
Magnitude = the absolute size or strength of an earthquake
What is intensity?
intensity is the severity of an earthquake at a certain location
what does magnitude depend on?
it depends on the length and breadth of the fault slip
What does a Richter scale measure?
the strength of an earthquake
What is the Moment magnitude scale?
the standard method for measuring earthquake size based on total seismic moment (energy released)
what bases the intensity of an earthquake?
the damage and the other observed effects on people and structures. varies from place to place within the affected area
what is the attenuation of ground motion?
attenuation is the decrease in ground motion (energy) received at a site with increasing distance from the epicenter
what determines the hazard level of an earthquake?
the probability of exceedance and return period
what is the probability of collapse?
the risk of collapse of a building when subjected to an earthquake or ground shaking that is larger than what we designed for
what two factors need to be considered when designing resistant earthquake design?
- buildling fragility curve
- hazard curve
what three characteristics can cause seismic damages?
earthquake, site, and structural
which three factors make up the complexity of earthquake ground motions?
- source effects
- path effects
- local site effects
1. earthquake fault movements are not uniform character
2. waves change
what is frequency?
defined as the number of complete cycles vibrating per second
from the top of one crest to the other
what is the gravitational acceleration?
g = 32.3 ft/s^2 or 386 in/sec^2
what do soft soil conditions do to a far epicenter?
it’ll amplify the ground motions regardless if its far and has less damage
what are the three earthquake ground motion characteristics?
- duration of the strong shaking
- amplitude
- frequency content
how is PGA commonly written out as?
usually defined as a percentage like 0.4g = 0.4*32.2
what is the design peak ground acceleration?
the maximum ground acceleration that is used by codes or seismic provisions for structural design
earthquake intensity
what is related to earthquake intensity?
distance to epicenter, duration of ground shaking, and site soil conditions
what is typically true of earthquake intensity from further epicenters?
generally, the further the epicenter, the less damage and intensity felt at the site, unless the site soft soil conditions amplify the ground motions
what is the modified Mercalli intensity scale?
a scale which measures earthquake intensities. lower rating is based on people’s feelings
are there special design provisions for buildings located near-fault sites?
yes, design codes tend to be more restrictive for structures at near-fault sites. two different categories for design depending on their distance from epicenter.
What is the Maximum Considered Earthquake? MCE
MCE is used in building codes as the maximum possible earthquake ground motion for consideration.
