Unit 5 2014 South Napa earthquake presentation
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Transcript of Unit 5 2014 South Napa earthquake presentation
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#shakemap
Interseismic and Coseismic Strain Analysis
South Napa Earthquake
Mag 6Aug 24, 2014
Lab Prep Assignment: Research and Reading
• In preparation for the next lab period, each student should select an aspect of the 2014 South Napa earthquake for which to do some research seismology, faulting, or damage (signup sheet is being passed around)
• Come to class ready to serve as the “expert” on your select topic for your 3-person team
• READ the short background document that I have e-mailed to you
Left blank to separate pre-activity intro slides from follow slides used during the actual class exercise after the class discussion.
Shaking-Related Hazard
Gray scale: Population per ~1 sq. km. from LandScan
Photo: Erol Kalkan, USGS
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://earthquake.usgs.gov/hazards/qfaults/map/
South Napa, CA, Earthquake – August 24, 2014 – M6
Photo: Thomas Holzer, USGS
Photo: Dan Ponti, USGS
Photo: Dan Ponti, USGS
Photo: David Schwartz, USGS
Photo: David Schwartz, USGS
Photo: Thomas Holzer, USGS
Photo: David Scwartz, USGS
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#scientific
http://www.unavco.org/instrumentation/networks/status/pbohttp://earthquake.usgs.gov/monitoring/gps/SFBayArea/svin/
http://www.unavco.org/instrumentation/networks/status/pbo/overview/P200
Interseimsic Velocities from Plate Boundary Observatory
Source:UNAVCO
Preliminary Coseismic Offsets for American Canyon Earthquake, Northern California Bay Area
Source:Nevada Geodetic Laboratory
Red star is earthquake epicenter
Blue arrows are ground displacements of permanent GPS stations calculated from data collected before and after the earthquake
Napa Earthquake interseismic velocities. Carefully draw the E–W and N–S velocity vectors associated with the three GPS sites shown as green dots in the map below. A negative east component is a vector pointing west, and a negative north component is a vector pointing south. The graphs are scaled in units of millimeters/year. Then draw the total horizontal velocity for each site, and determine the speed (that is, the length of the total horizontal velocity vector) of each site. You can determine the total horizontal velocity by one of the methods shown at right below .
Total horizontal speeds: P198_______________mm/yr; P200_______________mm/yr; SVIN_______________mm/yr
P198
P200
SVIN5 km
Map of the region west of the South Napa earthquake epicenter (red star). Gray dots are surface rupture mapped by Trexler and Morelan (2014).
Interseismic Velocities Prior to August 24, 2014 Name: __________________________
Maximum Interseismic Shear Strain Rate and Directions Derived from Three Years of GPS Data
Maximum shear strainRate Directions
Green: right-lateralBlack: left-lateral
Gray dots are mapped rupture from UC Davis. Red star shows the epicenter.
Log of maximum shear strain rate (1/y)
Napa Earthquake coseismic displacements. Carefully draw the E–W and N–S displacement vectors associated with the three GPS sites shown as green dots in the map below. A negative east component is a vector pointing west, and a negative north component is a vector pointing south. The graphs are scaled in millimeter units. Then draw the total horizontal displacement vector for each site, and determine the magnitude of the displacement (that is, the length of the total horizontal displacement vector) of each site, using one of the methods shown at right below.
Total horizontal displacement: P198_______________mm; P200_______________mm; SVIN_______________mm
P198
P200
SVIN5 km
Map of the region west of the South Napa earthquake epicenter (red star). Gray dots are surface rupture mapped by Trexler and Morelan (2014).
Coseismic Displacements circa August 24, 2014 Name: _______________________
Maximum Coseismic Shear Strain and Directions Derived from GPS Offset Data
Black dots are mapped rupture from UC Davis. Red star shows the epicenter.
Log of maximum shear strain Maximum shear strain
Directions
Green: right-lateralBlack: left-lateral
Earthquake Recurrence?
P198-P200-SVIN– Coseismic maximum shear
strain 1.05e-06– Interseismic shear strain
rate 0.30e-06 /yr– Earthquake relieved <4
years of accumulated shear strain
Surface Rupture was only ~12.5 km long
Source:Nevada Geodetic Laboratory
Red star is earthquake epicenter
Blue arrows are ground displacements of permanent GPS stations calculated from data collected before and after the earthquake