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DS710 - Active Traces of the Berryessa Fault

Symbols and Abbreviations

Three types of observations are often used to determine the location of the fault and indicate recency of movement: geomorphic evidence, creep evidence, and direct exposure of deformed geologic units either naturally exposed or in trenches. However, most of this fault zone lacks the cultural features needed to show the occurrence of creep, and as yet no trenches have been made across it . Therefore, the mapping of the active traces on this fault depends primarily on the interpretation of geomorphic features.

  

GEOMORPHIC FEATURES

Codes indicating strength of the evidence

G1  - strongly pronounced feature

G2  - distinct feature

G3  - weakly pronounced feature

 ?   -  additional uncertainty in tectonic origin

Codes

af -    alignment of multiple features as listed

as -   arcuate scarp

bfs -  back-facing scarp

bt  -   downthrown surface tilts back toward fault

dd -   deflected drainage

df  -   depression formed by some aspect of fault deformation, undifferentiated

dr  -   sag, depression formed in right stepover of fault trace

fs  -  faceted spur

gi  -   linear break (or gradual inflection) in slope

hb -  linear hillside bench

hv -   linear hillside valley

lr   -   linear ridge

ls  -    fault scarp height enlarged by landsliding

lv  -    linear valley or trough

n   -   notch

pr  -   pressure ridge in left stepover

rr  -    right-laterally offset ridge line

rs  -   right-laterally offset stream or gully

s  -    saddle

sb  -  broad linear scarp (implies multiple traces)

sc  -   scissor point, sense of vertical separation reverses

se  -   subsoil exposed

sl  -   linear scarp, undifferentiated

sn  - narrow linear scarp (implies dominant trace)

sp  - spring

ss  -  swale in saddle

vl  -  line of vegetation

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