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Historical Earthquakes: Issues and Biases. 1. Historic vs Instrumental Catalogs. Earthquake Intensities. ~100%g. x 10 =1000. x = 2. ~0.1%g. XI. II. Bakun Method. Biases. Intensity assignments = f(time). The Owens Valley Earthquake: Previous View. MMI V. - PowerPoint PPT Presentation
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Historical Earthquakes:Issues and Biases
1. Historic vs Instrumental Catalogs
Earthquake Intensities
Caption
II XI
~100%g
~0.1%g
x10=1000x = 2
Bakun Method
Biases
• Intensity assignments = f(time)
The Owens Valley Earthquake: Previous View
MMI V
Caption
V. Almost everyone feels movement. Sleepingpeople are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of containers
Biases
• Intensity assignments = f(time)1872 earthquake?
Caption
Caption
“Ground pervasively cracked,”Holden, 1887
“4-5’ subsidence along edge of Haiwee Meadows”Whitney, 1872
Southern segment,Vittori et al., 2003
Caption
Magnitude• L = 100 – 135 km• z = 15 – 25 km• s = 6 +/- 2 m (Beanland & Clark)
Mw1872 = 7.5 – 7.9
Biases
• Intensity assignments = f(time)1872 earthquake?
• Unreliable indicators: liquefaction, etc
Biases
• Intensity assignments = f(time)1872 earthquake?
• Unreliable indicators: liquefaction, etc• Reporting biases• Media “biases”• Higher structural vulnerability
Biases
• Intensity assignments = f(time)1872 earthquake?
• Unreliable indicators: liquefaction, etc• Reporting biases• Media “biases”• Higher structural vulnerability
Inflated magnitude estimates