Farallon Plate

• Existed 37 million years ago between North American and Pacific Plates
• Had subduction zone from Alaska to tip of South America

• Spreading Ridge Subduction 28 million years ago
• Subducted beneath North America

Remnants: Juan de Fuca, Cocos and Nazca plates

• Pacific plate contacts with North America
• 1200 km long with 4 distinct segments
• Northern, Central, South Central, and Southern Segments. Northern and South Central most active

• Second most powerful recoreded at 9.2
• 6 simultanious quakes at 8 Mw
• Rupture 600 mi long and 250 mi wide
• Caused avalanches, landslides, and liquifaction of ground beneath Anchorage
• Tsunami destroyed 80% of Kodiak Alaska
• Killed 131 (18 in Cali) and caused 400 mill in damage

• 8.2 with two aftershocks over 7
•  125 mile long Michoacan gap ruptured
• Mexico City built on lake bed and sediments, 5700 buildings damaged and collapsed 8000 killed

• South of Michoacan Gap, is the main future risk

• 1200 km subduction zone with no quakes in 200 years

• Ghost forests of trees
• Indian oral histories
• Japanese Tsunami reports
• Mw 9 in 1700

• 1200 km long rupture would cause a Mw 9 quake or higher from subducting Juan de Fuca Plate
• Scale of 9.5 Chilean quake in 1960

• Prehistoric Earthquakes
• Fault motion breaks sediment layers which are dated with carbon 14
• Can trace up to thousands of years, and predict better for future quakes

• 1330 year record to 670 A.D.
• 8 prehistoric, 2 historic in California
• Average of 132 years in Southern California, and 90 in Northern
• USGS Risk: 33% chance of Mw 7 w/in 30 years, 67% chance before 2018

• Occur 160-350 years appart
• Within clusters quakes are seperated by decades

• Mw 7.1
• Rupture 18.5 km deep and 42 km long
• 67 killed, 6 billion in damages

Reducing Loses

• Bulding practices
• Timing
• Location of Epicenter

Contributing to Losses

• Old buildings
• Soft sediment
• Liquifaction

• Big Quakes caused by a series of small faults
•  L.A. basin w/ Mw 7 quakes
• Worst Case: San Andreas 8+ cause a 7+ directly under L.A.

• Over 32 km in length
• Reverse fault in San fernando Valley
• Mid sized quake caused extensive damage