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