Sylmar Earthquake About: When: 6:00 A.M. February 9, 1971 Where: San Fernando Valley What: Ruptured segment of the San Fernando Fault Zone. Magnitude 6.6
Damage 65 people died $500 million in damage Two hospitals were destroyed Freeway Interchange Collapsed
The Whittier Narrows Earthquake About: When: 7:42 A.M. October 1st, 1987 Where: San Gabriel Valley What: Slip on a blind thrust fault. Magnitude 5.9 and 5.3
Damage 3 people died $358 million in damage
Loma Prieta Earthquake About: When: 5:04 P.M. October 17th, 1989 Where: The greater San Francisco Bay Area What: Reflected seismic waves
Damage 63 people died & 3,757 were injured $6 billion in damage Cypress Street Viaduct San Francisco-Oakland Bridge
Northridge Earthquake About: When: 4:30 A.M. January 17th, 1994 Where: San Fernando Valley What: Blind Thrust Fault
Damage 51 people died & 9,000 were seriously Injured $44 billion in damage 22,000 people left homeless, 25,000 dwellings uninhabitable, 9 hospitals lost, 9 parking garages collapsed, 9 bridges collapsed, portions of 11 major roads closed
Total Damages and Costs • Over the past 23 years the costs of these 4 earthquakes has been a crushing blow for California • The total number of deaths is estimated to be 188 • The total number of injuries is roughly estimated to be 8,804 • The estimated costs of damage due to these earthquakes is $31,531,000,000
Seismic Retrofitting • Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. • The key elements of seismic retrofitting are the levels of modifications and the types of modifications
Levels of Modification • Public Safety: the number one goal is to ensure that in the event of an earthquake, a building will not fall on the people inside or the people passing by. Building will need to be replaced • Structure Survivability: Structure stays for so people can exit in the even of an earthquake. After the quake it will need extensive repair but no need for replacement. • Primary Structure Undamaged: Only cosmetic repairs necessary. • Structure Unaffected: Nothing damaged. Used for historic structures.
Types of Modification • Hybrid Solution: Ductile reinforcement and joining of rigid plates and beams • Isolation: Required for large masonry buildings. The building is separated from the actual foundation. The two are joined by steal or reinforced concrete beams. • Dampers: Absorb the energy of motion and turn it into heat. Helps to reduce the damage of the initial shock. • Reinforcement: Adding strength to the original structure. The most common form of Seismic retrofit.