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Introductory lectures
G-R law, risk vs hazard, christchurch case study
25
Geology
05/21/2015

Term
 what is the pattern of the ratio of smaller faults to larger faults?
Definition
 the pattern of the ratio of smaller faults to bigger faults is consistent. This means that if there are 10 faults of magntiude 6 and 1 fault of magntiude 7, there will be 100 faults of magntiude 6
Term
 what is risk?
Definition
 risk = probability * consequence
Term
 what is the difference between the probability of an event and the existing risk of an event
Definition
 the probability of an event is just the liklihood that it occurs. Risk takes into account the consequences of it occuring
Term
 the estimation of rockfall risk he gave us is  Risklol = PH * PS:H * PT:S * VD:T what is PH?
Definition
 in the equation Risklol = PH * PS:H * PT:S * VD:T PH is the annual probability of of rockfall-iniating event i.e. earthquake
Term
 Risklol = PH * PS:H * PT:S * VD:T what is PS:H
Definition
 Risklol = PH * PS:H * PT:S * VD:T PS:H is the probability that a person, if present, is in the path of the boulder. This is asking: how many homes will get hit by boulders?
Term
 Risklol = PH * PS:H * PT:S * VD:T what is PT:S
Definition
 Risklol = PH * PS:H * PT:S * VD:T PT:S is the probability that a person is present when the event occurs. This changes if it's day and people are at work away from thier homes, or if it's night and everyone is asleep in thier homes
Term
 Risklol = PH * PS:H * PT:S * VD:T what is VD:T
Definition
 Risklol = PH * PS:H * PT:S * VD:T VD:T is the probability of a person who in the path of the boulder being killed. it's a "V" because that's a question of vulnerability, not probability.
Term
 2 ways risks are reduced: what does Mark think of each?
Definition
 2 ways to reduce risk from geohazards: 1. traditional hard engineering, trying to change the land to fit our interests. expensive, difficult, futile, and dangerous 2. changing our vulnerability to the existing threat. land use planning, better structures, better evacuation plans, avoiding dangerous areas
Term
 faults are like fractals. what implication does this have for predicting seismic hazard?
Definition
 because the ratio of smaller to larger faults is constant, we can look at the history earthquakes caused by small fualts, and predict where large faults will be.
Term
 predicting geohazards comes relies on measuring statistics of past events, and then using them as probablities of future events. what are three problems with this method?
Definition
 the method of looking at the history of geohazard events and using that to predict the future has three problems: 1. the past isn't perfectly indicative of the future. changes over long time scales, like climate change need to be considered 2. catastrophic events may have return time that are longer than the history we can confidently analyze 3. the third problem isn't a scientific one, but a human one. We are often incentivized to plan for shorter time scales than we have data for. even if we know a hazard is coming in 200 years, we may only care about the next election cycle, or a couple generations
Term
 what law says occurance interval is 1/10 for earthquakes as you go up an order of magnitude? i.e. there are 1/10th as many magnitude 8's as magntiude 7's
Definition
 the G-R law says that earthquakes are 1/10th as likely as earthquakes one unit of magnitude lower
Term
 difference between hypocenter and epicenter?
Definition
 the hypocenter is the source of the earthquake in three dimensions. the epicenter is a pair of coordinates above the hypocenter
Term
 there was always a fault underchristchurch, but we didn't see much activity 2000-2010. Then we started to see a ton 2010-13. beyond the fact that large earthquakes spawn aftershocks, what is happening?
Definition
 the reason seismic activity jumped up so high in christchurch is a story of stress redistribution. also, earthquakes tend to cluster over time
Term
 is rupture velocity magnitude dependant?
Definition
 rupture velocity isn't magnitude dependant
Term
 if you are closer to the epicenter of an earthquake, how does this affect duration of shaking?
Definition
 if you are closer to the epicenter of an earthquake, the duration of shaking is generally longer
Term
 where is the most extreme shaking from a fault rupture
Definition
 although shaking last longer near the epicenter, shaking is most extreme at the ends of a rupture
Term
 why is it irresponsible to build a suburb in the area bexley is?
Definition
 the ground bexley was built on liquifies every 75-100 years
Term
 4 imporant question to answer about fault rupture damage to forecast earthquake hazards, design sufficiently resilient structures, land-use reccomendations, and interpreting paleo-earthquakes in the record
Definition
 4 important questions to answer about fault rupture damage 1. relationship between earthquake magnitude and surface displacement 2. thresholds between surface cracking and folding 3. width of deformation zone 4. return times of earthquakes
Term
 if we can understand the relationship between fault rupture damage and earthquakes, what does this help us do? 4 things
Definition
 understanding the relationship between earthquakes and fault ruptures allows us to: 1. forecast earthquake hazards 2. make informed reccomendations for land use planning 3. design resilient structures  4. understand what rupture signals in the geologic record are telling us about earthquakes
Term
 is surface rupture length the same as fault length?
Definition
 surface rupture length may not be indicitive of fault length, which is the length of the whole fault
Term
 Mark's team measured surface slip from the darfield earthquake. what did they find?
Definition
 when Mark's people looked at surface slip from the darfield earthquake, they found there was large wavelength folding as well as discrete, more noticeable fracturing. if you just look at the more obvious fracturing signal, you miss the larger displacements and will underestimate displacement
Term
 how does the nature of surface ruptures make it easy to underestimate the displacement from an earthquake?
Definition
 the reason it is easy to underestimate displacement from an earthquake by looking at surface ruptures is that surface ruptures cause the classic fractured ground signal as well as more subtle, large scale bending. it's easy to come across the fracturing and measure it and think you are done, and miss some of the signal
Term
 what is SRL
Definition
 SRL is surface rupture length
Term
 why was the most damage caused by the second strongest quake in the canterbury earthquake sequence?
Definition
 the reason the second strongest quake in the canterbury earthquake sequence caused the most damage is becuse it was closer to CBD
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