**** Study Sessions:MONDAY, APRIL 28TH; 6:00-8:30 PM; WEBSTER 16THURSDAY, MAY 1ST; OPTIONAL ATTENDANCE – CLASS TIMEFRIDAY, MAY 2ND; 2:00-3:00 PM; WEBSTER 17Chapter 8: Earthquakes (continued) Why would earthquakes with nearly the same intensities (magnitude) produce such different results?o Ground material! o What kind of shakingo How buildings are built/quality of materialso The ground can amplify the shaking. Building on bedrock is the best Building on landfill is the worst (San Francisco Airport)- Amplifies most and collapses on itself Building on mud is bad- Mud liquefieso Liquefaction Ex. Loma Prieta (1989) Clay grains are aligned like a card house (deck of cards)- True quicksando Depth of focus Kobe and Northridge (10 mi & 11 mi respectively)o Duration of shaking Kobe (20 sec) and Northridge (15 sec)- Shorter than Nisqually but were combined with lack of proper building codesVideo on Earthquakes Northridgeo Los Angeles:  Many injured, 57 dead January 17, 1994 Same date and magnitude as Japan earthquake 11 freeways down – those specifically that had not been strengthened forearthquakeso Kobe: 15 miles underground Up and down then sideways (wave types) Morning Show was first anyone saw of Japan’s Seismometers – 3 to 5 around Kobe, knocked out in Kobe Broken gas mains started intense fires everywhere in Kobe Epicenter – just southwest of Kobe Hundreds died in fires alone Even emergency tanks underground were not enough for firefighters for the large amount of fires Nagata – market arcade surrounded by houses. Many dead in homes. Worst damage. Arcade was built extremely strong and held up; fed homeless following earthquake, etc. Entire community burnt to ground. >1000 people died. Nothing like this since WWII Tiles on roofing – heavy to protect against typhoons- Walls made of straw and mud- Stone ornament on every roof – heavy- Lethal for many > 5,400 dead, 300,000 without homes, 1,000,000 without food/water Cost: $147,000,000,000 of damage Shifted port-trade to Taiwan and North Korea- Liquefaction of Kobe’s docks- Only 3 shipping ports left after earthquake Bridge to island nearby- Epicenter directly below- Island shifted – bridge will need to be 1 meter longer- Bridge did not fall Mountains to north… alluvium basin to south- Waves hit mountains and are reflected back – intersections cause extreme damageo Causes & Similarities: Whole of Japan crisscrossed by faults and sits next to four plates that come together Both rather unlikely earthquakes; neither city lies on a fault exactly New fault found in Kobe by professor at a Japanese university Recently calculated that blind faults are located everywhere around LA Shaking in Kobe ~ shaking in northern part of San Fernando Valley Building “melting” usually caused by first floor failures (open lobbies, garages, offices, etc.)- Some due to “soft floor” in the middle of a building – building “pancaking”o Nearly an hour to pinpoint epicenter; computer basically said, “ground moving intoo many places all at once so this is obviously not possibly happening” Seismometers of both Japan and America were not sophistication enoughto cope with the size and intensity of these earthquakeso “Earthquakes do not kill people, buildings do.”o Early detection already in place Kobe – as soon as P-wave is detected all trains brought to a stopo Tiny seismometers – automobile airbag technology; not sensitive enough for small normal ground motion, but great for huge shakeso Smart Meters – Tokyo Gas. Shuts off gas to house as soon as shaking starts Prevent