Lecture 7 - Tectonic Hazards Flashcards
How is the magnitude of an earthquake determined?
By the logarithm of the amplitude of waves of the earthquake 100km from the epicentre
Who was the Richter magnitude scale developed by, in what year and why?
By - Charles F. Richter
When - 1935
Why - Mathematical means of comparing the size of earthquakes in Southern Cali
If an M7 earthquake produces 10x more ground shaking than an M6, how much more does it produce than an M5?
100x
The Haiti earthquake of January 2010 had an epicentre South west of Port-Au-Prince, at a depth of what? And what was magnitude?
M7
Depth - 13km
How many people died in January 2010 Haiti earthquake and left homeless?
230k dead
1.5milli homeless
(US Agency for International Development)
Name an ancillary hazard of the January 2010 Haiti earthquake?
Cholera: killed 8.3k and 650k suffered from it
Similarly to Haiti, Christchurch had an earthquake in 2010. Near Darfield, how deep was it, what was magnitude an how many dead?
Depth - 10km
M7.1
Dead - 0
Cost to insurers 3 billion
2011 Christchurch quake was smaller at M6.1, how many died?
181
100k buildings damaged
Although 2011 Christchurch quake smaller than 2010 quake, name 5 reasons it was more deadly?
- Epicentre closer an shallower at 5km
- Happened at lunch, weekday, people work in business centre
- Buildings weakened from previous
- Peak ground acceleration high, almost impossible to stay intact
- Liquefaction greater than 2010
Analysis of plate boundaries and associated earthquakes can how develop what?
Hazard maps
What is seismic deformation?
When an earthquake ruptures, it creates two types of deformation, static and dynamic
What is static deformation?
Permanent displacement of the ground due to an event
What is elastic rebound?
Where previous linear features display increasing displacement near the fault
In the imperial valley 1940, elastic rebound caused what?
Offset regular rows of oranges by 6m
Different types of seismic waves produce the same end result what is this?
Vibrating ground
On Tuesday January 17 1995 5:46am an earthquake struck Kobe and Osaka, what was magnitude and people affected, cost?
7.2M
People affected - 300k
Damage -$147bn
180k buildings damaged
What did Roger Bilham quote?
Earthquakes do not kill people, buildings do…
What are the 3 main types of building failure from earthquakes that can be prevented?
- Detailing
- Soft Storey Collapse
- Shape and Steel failures
What is detailing?
A term to describe the steel in a reinforced concrete member
Poor detailing is the cause of a large proportion of failures in older concrete, why is this?
Due to the lack of links or inadequate cover by links
In an earthquake what will a concrete beam/column do?
Vibrate causing the concrete to crack if not restrained
Why must stiff elements in buildings be made stronger?
They will attempt to resist larger earthquake forces than flexible elements in the same structural system
What is soft storey collapse?
When a building has one floor weaker than the others
A floor fails and flattened by weight of those above
Mid storey collapse due to differences in stiffness or ductility result in what?
Collapse of a whole floor so this mean whole building fails
