Term
| when we are looking at buildings, our focus is on what measure of earthquake intensity? |
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Definition
| when we are looking at buildings, we care about the intensity of shaking. Specfically, the amount of energy transferred at different frequencies |
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Term
| building code for non-critical vs critical infrastructure related to earthquakes |
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Definition
building code for non-critical buildings: they must to able to survive 1 in 475 year shaking
for critical buildings (post-disaster importance, like shelters and hospitals): they must be able to survive 1 in 2,500 year shaking |
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Term
| if you are in a tall building, you hope the shaking is at ____ frequency |
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Definition
| if you are in a tall building, you hope the shaking is at shorter frequency |
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Term
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Definition
| the key observation from that graph is that there is more accleration on the high frequency/low period side of the curve |
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Term
| how do soft layers in the ground respond to shaking? |
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Definition
| soft layers in the ground amplify shaking, but they eat some high frequency waves |
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Term
| how do harder layers in the ground react to shaking? |
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Definition
| harder layers in the ground allow waves to travel further, and don't absorb any high frequency waves |
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Term
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Definition
| the takeaway from this graph is that accleration was greater than the 2,500 year return at most frequencies. the fact that people walked out of buildings meant to withstand 475 year shaking is really fortunate |
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Term
| does the current building code take post-event fuctionality into account? |
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Definition
| the current building code doesn't take post-event functionality into account. buildings up to code can stay upright during shaking, but must be torn down afterward. Post-event functionality means they can be repaired after shaking |
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Term
there was talk of changing the Z factor in the building code, (higher Z code=more resilient to shaking) from .22-.3 or 3.5
how much would this bring up construction costs? (give a range) |
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Definition
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Term
| what two peices of information do we use to figure out how many blind faults there are? |
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Definition
| to figure out how many blind faults there are, we start by connecting magnitude to chance of surface rupture. using the G-R law, we can solve for many faults there are that move but don't have a signal at the surface |
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Term
| why do fewer magnitude 7 earthquakes in NZ cause surface ruptures? 2 reasons |
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Definition
2 reasons why an above average % of magnitude 7 earthquakes come from blind faults in NZ
1. NZ geology close to surface has more weak rocks and soft layers that simply shift and absorb the energy instead of bringing rupture to surface
2. NZ is a subduction zone, so many earthquakes originate deeper |
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Term
| how do we find blind faults we haven't mapped yet? |
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Definition
| to find blind faults we haven't mapped, we use the G-R law. log(displacement) vs number of events is a straight line |
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Term
| Sesimic hazard model takes these two factors into account |
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Definition
| the seismic hazard model is a function of siesmic source data and the expected site response |
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Term
| what three things go into figuring out seismic source data? |
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Definition
the three things that go into figuring out seismic source data are:
1. distributed seismicity
2. mapped faults
3. Floating sources, which are faults we haven't mapped but we know are there b/c of the G-R law |
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Term
| expected site response takes what three things into acount? |
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Definition
expected site response takes into account these three things
1. where site is compared to rupture
2. site's vulnerability
3. attenuation, which is weaking of signal over time |
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Term
| the sesimic hazard model must take into account the distribution of how different sites will response to a certain shaking intensity at ____ |
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Definition
| the sesimic hazard model takes into account how different sites will response to a certain level of critical shaking at different frequencies |
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Term
| knowing the magnitudes and recurrance intervals of faults isn't enough to create meaningful seismic source data. other information do you need? |
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Definition
| knowing the magnitudes and recurrance intervals of faults isn't enough to create useful seismic source data. To get risk of anaylsis from magnitudes and recurrence intervals you need to use the G-R law to find a magnitude-frequency relationship |
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Term
| the goal of the seismic hazard model is to produce what? |
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Definition
| the goal of the siesmic hazard model is to produce a temporal distribution of how a range of sites will react to various shaking intensities at various frequencies. |
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Term
| sesimic source data relies on what three peices of informatuion? |
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Definition
| seismic source data relies on surface rupture length, subsurface rupture length, and moment magnitude (Mw) |
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Term
| what does the term "characteristic earthquakes" refer too? |
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Definition
| the term characteristic earthquake refers to faults that produce earthquakes at regular recurrence interval, and where displacement is similar every event |
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Term
| what does the christchurch hazard deaggregation plot tell us? |
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Definition
| the christchurch hazard deaggregation plot shows us that a lot of hazard in CC comes from blind faults. If a magnitude 6 earthquake hits CC, there's a 50% chance it came from a blind fault. If a mag 9 quake hits CC, there is a 90% chance it came from a blind fault |
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Term
| what is the goal of fault-based seismic hazard analysis? |
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Definition
| the goal of fault-based siesmic hazard analysis is to take geolgic data and turn it into a recurrance interval and slip rate |
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Term
| what case study did we look at that involved segmented faults slipping in tandem? |
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Definition
| the darfield earthquake involved 7 faults slipping in tandem |
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Term
| what is seismogenic thickness? |
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Definition
| seismogenic thickness is the distance from the deepest part of the rupture to the surface |
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Term
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Definition
| down dip width is the width of a fault measured in the down-dip direction |
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Term
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Definition
| seismic moment is a measure of the strength of a quake based on area of fault rupture, average amount of displacement, and force required to overcome friction |
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Term
| what is the measure of a width of a fault measured in the down dip direction? |
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Definition
| the measure of a width of a fault measured in the down dip direction is called down dip width |
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Term
| what is do we call the depth of the deepest part of a rupture? |
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Definition
| the depth of the deepest part of the rupture is seismogenic thickness |
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Term
| this quality of a quake is a function of it's rupture area, average displacement, and the frictional force overcome? |
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Definition
| seismic moment is a measure of a quake's size based on the area of fault rupture, the average amount of displacement, and the frictional force that was overcome |
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Term
| how do we get the surface slip rate of a fault? |
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Definition
| the surface slip rate of a fault is based on geological observations combined with paleoseismology |
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Term
| how do find sesimogenic thickness? |
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Definition
| to find seismogenic thickess, use a combination of geophysical observations and studying earthquake distributions |
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Term
| how do we calculate down dip width? |
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Definition
| down dip width is a function of surface dip and siesmogenic thickness. DDW is the down dip width, which is the width of a fault in the down dip direction |
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Term
| how do you find the fault plane area? |
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Definition
| the fault plane area is DDW*length of rupture |
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Term
| how does one derive MO and Mw when doing a fault-based seismic hazard analysis? |
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Definition
| MO and MW are dependent on fault area, slip, and sesimic moment |
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Term
| how do we find subsurface single event displacement (SED) and subsurface slip rate (SR)? |
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Definition
| we use surface SED and surface SR to find subsurface SEB and subsurface SR |
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Term
| what are the nine steps in fault-based sesimic hazard analysis? |
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Definition
the steps in fault-based seismic hazard analysis
1. map the fault
2. see if the fault is segmented, see if it moves in tandem with other faults. Remeber that the darfield quake invoved 7 faults slipping together
3. Geology/paleoseismology step. Find the surface slip rate (SR)
4. geophysics/quake distribution analysis step. find the sesimogenic thickness
5. use seismogenic thickness and dip at surface to find down dip width
6 use down dip width and length to find fault plane area (DDW*L=fault plane area)
7. find Mw and MO with fault area, slip, and seismic moment
8. use surface SED and RL to find subsurface SED and RL
9. use subsurface RL to find recurrance interval
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Term
| 3 qualities of good earthquake forecasting |
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Definition
good earthquake forecasting is
1. publicly availible
2. continously updated
3. provides information at different timescales |
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Term
| draw a profile of a fault indicating down dip width, hanging wall, and footwall |
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Definition
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