Introduction to Fault Scarps

Unit 3: Introduction to

Fault Scarp Analysis

UNAVCO

Scarp morphology

Modified from Wallace, 1977

Types of scarps

Modified from Stewart and Hancock, 1990

Types of scarps

Modified from Stewart and Hancock, 1990

Scarp morphological evolution

Modified from Stewart and Hancock, 1990

Example scarps

USGS, Chris Crosby

Hebgen Lake (1959) Wasatch Fault (~1985)

El Mayor-Cucapah (2010)

Profile extraction

Chris Crosby

Example profile

Indiana University Geologic Field Station

Rupture length – maximum displacement

Modified from Wells and Coppersmith, 1994

Rupture length – magnitude

Relationship between displacement length and earthquake magnitude M = Magnitude L = Length

All rupture types M = 5.08+1.16*log(L)

Strike slip rupture M = 5.16+1.12*log(L)

Reverse or thrust rupture M = 5.00+1.22*log(L)

Normal rupture M = 4.86+1.32*log(L)

• Variables: fault scarp eroded material height, m (H) erosion rate, m/yr (ER) Recurrence interval, yr (RI)

• H / ER = RI• Use many estimated erosion rates to find

a recurrence interval that seems representative

Recurrence interval

• Variables: dx: spacing between measurements dt: time between each calculation step k: transport rate of sediment

• Israel: 0.1 m2/ka• Basin and Range: 1 m2/ka• California/Michigan: 10 m2/ka

• Use the given spreadsheet, variables above, and your profile to model hillslope diffusion.

Hillslope diffusion