Geology: Chapter 4 (Tsunamis)
Explain how a Landslide can cause a Tsunami:
Submarine landslides occur when landslides occur underneath the water or from the surface into water; Displaces water vertically which causes Tsunamis.
Define "Run Up":
Furthest horizontal and vertical distance of the largest wave
What types of regions are at risk for Tsunamis?
-All ocean and some lake shorelines face a risk -Greater risk for coasts near earthquakes, landslides, and volcanoes. -Greatest risk in areas near or across from subduction zones.
2004 INDONESIAN TSUNAMI
-December 26, 2004 -9.1 Magnitude earthquake -Subduction zone -Little education about Tsunamis -No Tsunami warning system in place
How can we minimize the Tsunami hazard?
-Detection and warning -Structural controls -Construction of Tsunami Run up maps -Land Use -Education -Tsunami ready status
Explain how an Earthquake can cause a Tsunami:
-Earthquake must be a min. of 7.5 magnitude for enough water displacement to occur -EQ rupture uplifts the seafloor -A dome forms on the surface of the water above the fault -Dome collapses and generates tsunami wave -Waves radiate outward
-Can humans prevent/control Tsunamis? -Does human activity affect the frequency or magnitude of Tsunamis? -How have humans increased our susceptibility to the consequences of tsunamis?
-No, humans cannot prevent/control Tsunamis -Human activity does NOT affect freq./magn. -Our increased use of shoreline increases the consequences of a Tsunami
2011 JAPANESE TSUNAMI
- March 11, 2011 -9.0 Magnitude Earthquake -18 ft. seawall -Some waves reached 3 mi. inland -Subduction Zone -Secondary Damage: Nuclear incidents and radiation releases
What are the 3 main secondary effects of Tsunamis?
1. Fires (from ruptured gas lines) 2. Contaminated water supplies 3. Disease
What are the 2 main primary effects of Tsunamis?
1. Flooding 2. Erosion (debris erodes both landscape and human structures)
How do Tsunami waves act in the deep ocean vs Near Land?
Deep ocean: -Dome shaped -Travel up to 600 mph -Spacing of crest is large (low frequency) Near land: -Wave loses speed, gains height -Depth of ocean decreases which slows waves -More water piles up which increases amplitude and frequency
Distant vs. Local Tsunamis
Distant Tsunamis: Travel out across (thousands of km.) the deep ocean at a high speed; strike remote shorelines; little loss of energy. Local Tsunamis: Heads the opposite direction toward the nearby land; can arrive quickly after an earthquake; gives residents little warning time.
What are the two main causes of Tsunamis
Earthquakes and Landslides
How do we define risk?
Risk= (prob. of event) x (consequences)
