Unit 2 Flashcards
Why is it important to study intensity when an earthqauke happens?
Intensity determines where the earthquake is most severe. Instrumental intensity helps forms shake maps which highlights points most vulnerable to shaking. Understanding how different structures and regions respond helps cut down on causalities.
What is an aftershock?
The final stage of an earthquake. Usually smaller in mag. than mainshock.
What is the relationship between an aftershock and stress transfer?
Aftershocks (mini earthquakes) are caused by the releases in pressure that happens during an earthquake. This break in pressure travel outwards and is a transfer of stress (stress transfers). These many occur in the hundreds and seconds or years after mainshock and in surrounding fault lines.
What did the 2004 Parkfield earthquake tell us about predicting earthquakes?
That we can’t predict them regardless of pattern. The only thing we can predict is the probability.
Why didn’t the M7.8 Haida Gwaii earthquake cause a significant tsunami?
Because it was a transform earthquake where the movement was side-to-side vs up and down
What is the difference between wind and tsunami waves?
Tsunami waves are usually caused by large disturbances (e.g. earthquakes), are significantly larger (200km wide vs 150m wide), and travel much quicker.
What implications does the size, speed, and source of generation of tsunamis have in regard to the hazard they present?
Tsunamis represent a significant hazard as they are difficult to adequately predict and prepare.
What happens to volcanic gases when the pressure is reduced as magma approaches the surface?
First, there is a reduction of pressure that causes gases to exsolve from magma as bubbles that expand.
Then, the bubbles cause the volume of magma to increase.
How does the reduction of pressure as magma reaches the surface affect volcanic eruptions?
As the pressure reduces during the production of bubbles, pressure is then transferred to the rock which can cause a violent explosion. The type of magma (felsic has high viscosity and gas levels), the explosion can increase.
What are typically the first indications that a once-dormant volcano may erupt again soon?
increased seismic activity
ground deformations
(gas emissions, changes in thermal, magnetic, and hydrologic conditions)
Why is it useful to get a sample of eruptive material early on during the cycle of a new volcanic eruption?
inform risk level based on magma chemistry (e.i. viscosity, gases) as well as track changes
How are seismologists able to identify movements within tectonic plates?
Satellite GPS measurements that identify deformations
Describe the current state of the subducting Juan de Fuca plate at the boundary of the North American plate.
-lower portion is warmer and continually sliding causing compression and elastic shortening
-central portion slips periodically
-higher portion is cool and stuck (will move upon the occurrence of large and infrequent earthquakes)
What does the current state of the Juan de Fuca plate suggest in terms of a future earthquake?
-the pressure of the “locked zone” will eventually become too much
-there is an impending large earthquake
-the periodic slipping could cause this earthquake any moment
What are some key points when creating a tsunami education program?
-tsunami characteristic (signs, including wave run-up)
-probability
-travel routes, evac plans (identify hazards)
-detection (warning systems)
-preparedness (first-aide, water, food supplies)
-developing person plan
-recovery efforts
