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