Geology Reference
In-Depth Information
Coseismic Uplift, Peru
Te r
0
T
obs
1
+ SL
up
2
= Up
tot
1
10
1
0
Te r
1
T
obs
1
Up
tot
2
Te r
2
T
obs
2
Te r
0
5
5
Te r
1
SL
up
2
Up
tot
1
SL
up
1
Te r
0
0
0
Uplift
events
T
2
T
1
T
0
Fig. 6.10
Coseismically uplifted
marine abrasion platforms.
A. Schematic pattern of abrasion
platform formation and coseismic
uplift during a rising sea level,
yielding staircase of marine terraces
(Ter). The total tectonic uplift (Up
tot
)
in each event represents the sum of
the observed offset (T
obs
) of the
platform plus the sea-level rise (SL
up
)
that occurred since the preceding
uplift event. In this example, 3 m of
sea-level rise must be added to the
2 m of apparent coastal uplift shown
by the vertical separation between
successive terraces. B. Uplifted
abrasion platforms on the Peruvian
coast showing the vertical height
difference between platforms, each
of which is attributed to a large
subduction-zone earthquake.
Cosmogenic exposure ages are
shown for two dated platforms.
Modified after Bourgois
et al.
(2007).
Inset shows late Quaternary
sea-level rise. Modified after Fleming
et al.
(1999). C. Total rock uplift as
the sum of the apparent uplift
(observed terrace elevations) plus
sea-level change. During the past
8 kyr when sea level was steady, the
total and apparent rock uplifts are
equal, but 120 m of sea-level rise
between 20 and 8 ka more than
doubles the total uplift during this
earlier interval. Without accounting
for sea-level change, the Pleistocene
rate (dashed line) would appear
slower than the Holocene rate.
1000
500
0
A
Time (years)
100
7.2
4.4
0
-40
-80
-120
6.9
75
6.3
3.9
7.4
8.1
6.6
20.4±2.4 ka
18 15 12 9
6
3
0
Years BP (ka)
50
mean long-term
rock-uplift rate:
~10 mm/yr
mean recurrence
interval:
~1300 yr
3.4
uplift per
quake (m)
8.6
3.3
9.6
6.3
8.1±1.8 ka
25
4.4
5.2
0
0
100
200
300
400
500
B
Distance from coastline (meters)
sea-level rise
200
120
m
rock-
uplift
rate
total
rock
uplift
14
mm/yr
100
5
mm/yr
apparent
rock uplift
0
0
5
10
15
20
25
C
Age before present (ka)
