modern
DESCRIPTION
With a sedimentation rate of ~1 m/100 yrs, and individual clastic units representing on average 5-10 years, we can distinguish events that are likely separated by decades. Here are two earthquakes separated by just 20-30 cms , and thus likely 20-30 years (as the C-14 shows). - PowerPoint PPT PresentationTRANSCRIPT
With a sedimentation rate of ~1 m/100 yrs, and individual clastic units representing on average 5-10 years, we can distinguish events that are likely separated by decades.
Here are two earthquakes separated by just 20-30 cms, and thus likely 20-30 years (as the C-14 shows).
modern
1500 A.D.
1500 B.C.
3000 B.C.
YoungSection
Old Section
BSSA: Biasi, 2002; Fumal, 2002; Scharer, 2007
MiddleSection
12 meters44 clastic layers15 earthquakes
4 meters44 clastic layers14 earthquakes
Composite Stratigraphic Column
Dated Interpolated
Calendar Year (A.D.)
Cum
ulati
ve T
hick
ness
(cm
)Cu
mul
ative
Fre
quen
cy
Sedimentation EventReturn Interval
Clastic Accumulation Rate(cm/yr)
37 yr
0.6 cm/yr
Young Section
Earthquakes
2 cm/yr
12 yr236 yr
0.4 cm/yr
Variation around avg thickness (25 cm) - Modeled Dates
-40
-20
0
20
40
60
80
100
500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
Calendar Year
Clas
tic (c
m)
clastic
WW Young - Clastic Sedimentation Rates
0
200
400
600
800
1000
1200
500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
C14 dated
interp
eqs
Age of debris flow layer is age of underlying peat.
avg avg
Age Range # eqs # DF layers
DF thickness DF RI
634 890 5 13 43 20
890 1191 2 6 15 50
1191 1338 1 1 65 147 W6
1338 1857 5 21 16 25
Starting w/ W13
Pallett Creek
<1,600,000 <130,000 <15,000 <1500%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
<0.2 0.2-1.0
1-5 >5
Age Category (years)
Slip rate category(mm/yr)
• Of the 111 UCERF-2 slip rates we can associate with USGS Quaternary Faults Database slip rate categories, 96 UCERF rates fall in the consistent USGS category, 6 UCERF rates are too high, and 9 UCERF rates are too low.
• We need to check the 15 that are not consistent and do some work to associate the rest of the UCERF rates with their USGS categories so we can check their consistency.
• We can use the USGS Quaternary Faults Database to assign slip rate categories to UCERF faults that we don’t have slip rates for.