1906 San Francisco EQ ~7.8M 1811 New Madrid EQ ~7.7M V VIII II - III VI IX 200 km Modern shaking hazard map Magnitude is not the whole story… Intensity, and its relationship to how materials respond to seismic waves, is a large part of the case studies of individual earthquake events

Intensity is a direct response to ground shaking and varies with materials

Earthquake Case Studies Armenia (1988) – 6.9 M w/ 5.9 M aftershock (4 minutes later) ○ 25,000 killed Haiti (2010) – 7.0 M ○ ~300,000 killed San Francisco (1989) – 7.1 M (Loma Prieta earthquake) ○ 62 killed L.A. area (1994) – 6.8 M (Northridge earthquake) ○ 60 killed San Francisco CA (1906) – 7.8 M ○ Estimated 3000 deaths Michoacán, Mexico City (1985) – 8.1 M ○ 8000 killed Anchorage, Alaska (1964) – 9.2 ○ 123 killed Seismology became a serious field of study after this earthquake; secondary fires Four earthquakes with similar magnitudes (~7 M) but different levels of preparation and building standards earthquake intensity can be large even at a location far the earthquake focus ≥ 9 M earthquakes usually at subduction boundaries; secondary geologic events such as tsunami and liquefaction

Earthquake Case Studies Armenia 1988 Northridge 1994 Loma Prieta 1989

Armenia 1988 Northridge 1994 Loma Prieta 1989 Earthquake Case Studies Four earthquakes form modern times all with very similar magnitudes of 6.8 to 7.1 M All were in populated areas but death tolls were vastly different Death tolls don’t even tell the whole story, consider… Injuries Loss of infrastructure Loss of homes Health issues Long economic issues Quality of life

Earthquake Case Studies Armenia (1988) – 6.9 M w/ 5.9 M aftershock ○ 25,000 killed; 19,000 more injured, 500,000 homeless (~71%) ○ Major damage to most hospitals ○ Killed or injured ~80% of doctors/nurses ○ Major cause of death and injuries >>> Building collapse 314 collapsed, 614 demolished, only 24% remained useable ○ Prefabricated concrete buildings pancaked ○ Economic losses $4-16 billion US ○ Continent-Continent collision Illustrates (1) problems with poor construction methods and the need for proper building codes and (2) critical need to protect medial facilities, medical personal and first responders

Earthquake Case Studies Haiti (2010) – 7.0 M ○ ~316,000 killed, 300,000 injured and 1.5 displaced from homes ○ Collapse of poorly constructed buildings, including Parliament Building and parts of Presidential Palace ○ Seismic wave amplification due to poor soils/sediments ○ Triggered minor tsunami (killed 4) ○ Major sanitation issues after the earthquake ○ Left-lateral strike slip fault along Caribbean-North American plate boundary ○ Historic earthquake activity recognized Illustrates (1) problems with poor construction methods and the need for proper building codes and (2) underdeveloped country where government ignored warnings of earthquake hazards and vulnerability

Earthquake Case Studies Haiti (2010) – 7.0 M Presidential Palace before and after

Earthquake Case Studies Haiti (2010) – 7.0 M

Earthquake Case Studies Loma Prieta (1989) – 6.9M (updated to 7.1M) (World Series earthquake) 42 km (26 mile) section of San Andreas right-lateral strike slip fault ruptured, ~100 km south of San Francisco and Oakland Section of fault that failed… ○ left-stepping bend >>> reverse (compression) component in addition to strike- slip ○ represented a seismic gap (no recent activity) 63 killed; 3757 injured; 12,000 homeless $6 billion in property damage (you can lose more when you have more) Intensity of IX in marina district (soft sediment = enhanced ground motion) Buildings in Marina district partially collapsed Offset: 1.9 meters (6.2 ft) horz. 1.3 m (4.3 ft) vert. Majority of deaths due to collapse of Nimitz Freeway bridge Much structural damage due to soft sediment >>> enhanced ground motion (including freeway collapse); included liquifaction (sand boils etc.) Earthquake engineered buildings performed well, including hospitals and schools 51 aftershocks >3.0 w/in 24 hours, 87 over next 3 weeks

Loma Prieta (1989) – 6.9M

Earthquake Case Studies Northridge, CA (NW of Los Angles) (1994) – 6.7 M Earthquake occurred on a “blind” thrust fault (no surface expression of fault, fault was previously unknown) beneath the city Fault ruptured over eight seconds beginning at 17.5 km depth and propagated up to a depth of~ 5 km Domed (deformed) crust over an area of ~4000 km 2 Example of seismic event in a major urban setting that was prepared for earthquakes Maximum intensity of IX 60 dead, >7000 injured, 20,000 left homeless 40,000 buildings damaged Thousands of landslides over large area triggered by earthquake Freeway overpasses collapsed (7 sites), 170 bridges damaged Most seismically engineered buildings performed well, but some were significantly damaged Emergency response was adequate Illustrates the fact that some earthquake generating faults may go unrecognized even in a well studied area.

Northridge, CA (1994) – 6.7 M

Example of fault plane propagation, 8 seconds of rupture up the fault plane

Northridge, CA (1994) – 6.7 M

Earthquake Case Studies San Francisco, CA (1906) – 7.8 M ○ 3,000 killed ○ Rupture of 430 km of San Andreas fault w/ horizontal displacement of 6.4 meters ○ Epicenter near city ○ Buildings collapse on earthen fill areas ○ Major water mains and gas lines ruptured ○ Fire caused much of the loss of property (lack of water to fight fires) Seismology became a serious field of study after this earthquake including the pioneering work of Charles F. Richter at Cal Tech (Richter Scale dates to 1935)

Earthquake Case Studies Michoacán, Mexico and Mexico City – 8.0 M (19 Sept 1985) Focus/epicenter near coast 350 km (220 miles) west of Mexico City Two major aftershocks: 7.5 M (21 Sept) & 7.1 M (25 Oct) deaths, mostly due to building collapse (some estimates are ~35,000 dead) Most of damage and loss of life in Mexico City Minor tsumani, many landslides triggered by earthquake 30,000 injured, 100,000 homeless Happened on a work day Intensity at Mexico City was IX Why some much damage in Mexico City? ○ Mexico City built in a basin on unconsolidated sediments of ancient lake bed; basin surrounded by bedrock mountains ○ Enhanced ground motion >>> resonance (amplification of seismic waves) ○ Seismic wave reflection and interference ○ Some poorly constructed buildings Illustrates the fact that earthquake intensity can be large even at a location far removed from the earthquake focus

Michoacán, Mexico and Mexico City – 8.0 M (19 Sept 1985)

Earthquake Case Studies Anchorage, Alaska – 9.2 M Good Friday, 1964 Epicenter 120 km SE of Anchorage Motion on 1000km x 400km section, 520,000 km2 uplifted, uplift up to 11.5 meters, subsidence of 2.3 meters (relative to sea level) 128 killed Happened on a holiday, most people at home Major killer was tsunami (113 of 128), 67 meter high wave at Valdez Inlet 15 deaths in Cresent City, CA; curiosity seekers came out to see the tsunami ~ 30 blocks of building and home damaged/destroyed Major liquefaction (type of landslide) in the Turnagain subdivision (~130 acres, 75 homes) Major losses in the shipping and fishing industries ~$311 million in losses Subduction zone earthquake Illustrates the fact that ≥ 9 M earthquakes usually at subduction boundaries and that earthquakes can trigger secondary geologic events such as tsunami and liquefaction

Anchorage, Alaska (1964) – 9.2 M

Anchorage, Alaska (1964) – 9.2 M Tsunami liquefaction