Page 1

A Comparison of Disturbance Event Deposits from Cascadia Lakes to Marine Seismogenic Turbidites Ann E. Morey1, Chris Goldfinger1, Christy E. Briles2, Daniel G. Gavin3, Daniele Colombaroli4 and Jennifer E. Kusler3

Poster #T23E-2735

College of Earth, Ocean and Atmospheric Sciences

1College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis,OR, United States, 2School of Geography & Environmental Science, Monash University, Melbourne, VIC, Australia, 3Geography Department, University of Oregon, Eugene, OR, United States, 4Institute of Plant Sciences, University of Bern, CH-3012, Bern, Switzerland.

Briles et al., 2008

CT density

1.6 210

Pb(excess)

H

T1 T2

CASC 168:

H

500 (390-590)

0

Mag. Susc. (ln((cgs+2.1)/2) -10 200

1.2

T2a

fine detritus gyttja medium detritus gyttja coarse detritus gyttja with abundant macrofossils clay

50

100

H

T5b T5c 1.0

1950 (1870-2010)

H

T7

2230 (2150-2330) H

T8 CASC 189:

H

T8a

3500 (3300-3660) 3600 (3440-3760) 3890 (3720-4080)

200

(

Deep-Sea Marine Sites

H

3880 (3820-3980)

T10a Light

CASC 147:

5240 (5090-5370) 5390 (5240-5590)

T10b T10c

5740 (5590-5880)

T10d

H

300

3.0

6000 (5870-6120)

H

T10f

6900 (6780-7030)

4.0

(6970-7260) T13 5.0m (7530-7820) T14 T14a 7940 (7800-8090) CASC 32: 7100

H

CASC 9: 7670

( (

Swantown Marsh E

( (

!

Discovery Bay E Cultus Bay E

(

# *

8100 (8020-8180)

9820 (9630-9950)

6.0m (8990-9260) T17

CASC 88: 9190

(9070-9300) T17a

!

CASC 89: 9830

(9640-9990) T18

CASC 90: 10200 CASC 91: 10280 CASC 92: 10470 CASC 93: 10950 CASC 94: 10960 CASC 95: 10940

Coastal Lakes, Marshes and Estuaries

(

11600 (11390-11810) 12360 (12110-12420)

!

Washington !

(10350-10650) T20 (10880-11050) 7.0m T21 (10820-11080) T22

13310 (13190-13440)

H

13880 (13780-13990)

H

(

!

Laminations

H

7.0

H

LAKE

( ( (

(

!

(

Lake Sites in this Study

! ! !

! !

!

(

Triangle

` Lake ^

!

(

# * ## * ** #

Lake Washington: Lake Washington is a large (22 km by 5 km), moderately deep, steep-sided lake formed in a glacially carved basin in Puget Sound. Sidescan images show numerous sediment slumps and debris flows, and high-resolution seismic profiles show large retrogressive slope failures. Sediment cores from throughout the lake show sedimentary deposits with magnetic susceptibility signatures that can be correlated throughout the lake which have been interpreted as a result of shaking-induced sediment failures. Large local events on the Seattle Fault, as well as subduction zone events, appear to be recorded in this lake.

! !

!

!!

44°0'0"N

(

! ! !

! !

Oregon

!

(

!

!

!

!

(

Coos Bay E !

(

# *

Bradley Lake, OR: Bradley Lake is a dune-bermed coastal lake which produced a 4,600 year record of tsunami inundation.

!

CoquilleE

!

EBradley Lake !

!

!

(

E Sixes River !!

Triangle Lake, OR: Landslide-dammed lake of interest west of Eugene, OR in the Coast Range (207 m elevation). Recent coring resulted in a 6000 year old record with stratigraphic features of interest.

!

Rogue !

!

!

(

# #* *

` ^

(

M9907-33PC/TC

# *

Klamath

Legend

(

E

# * # * # *

# * # *

Trinidad

(

# * (

# *

(

# * # #* *

# #* * #*

E EEel River

126°0'0"W

!

RR0207 Cores M9907 Cores TN0909 Cores

` ^

SOIL 1

42°0'0"N

Strength Type

(kN/m3)

16

0

Cohesion Phi (kPa) (deg)

Mohr-Coulomb

20

10

20

34

Water Surface

Hu Type

B-Bar

Water Surface

Constant

0.3

Mat. Weight Causes Excess Pore Pressure Yes

40

60

80

100

120

140

Project

SLIDE - An Interactive Slope Stability Program

Upper Squaw Lake, OR: Upper Squaw Lake is landslide-dammed lake approximately 55 km east of Sanger Lake (930 m elevation). It has a large drainage area (~40 km2), and thus a very high sedimentation rate .

Analysis Description Drawn By

Scale

Date

Ü

1:672

Company File Name

8/9/2012, 8:37:41 PM

SLIDEINTERPRET 6.018

B. low cohesion

Bolan Lake, OR: Bolan Lake is located approximately 20 km NE of Sanger Lake. It is a spring-fed cirque lake (1638 m elevation) with a small drainage. Muslatt Lake, CA: A small landslide-dammed lake that is the most proximal site to the CSZ, located about 22 km east of Crescent City, CA.

Other Prospective Lake Sites Focus Lake Site With Existing Data

124°0'0"W

Sat. Unit Weight

Unit Weight (kN/m3)

Material Name Color

-20

Coastal Paleoseismic Sites

Humboldt Bay

Safety Factor 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00+

5 degree slope.slim

0.95

0.1

0.1

W

122°0'0"W

Safety Factor 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00+

Material Name Color

Available Data

Unit Weight (kN/m3)

Sat. Unit Weight (kN/m3)

Strength Type

16

20

Mohr-Coulomb

Cohesion Phi (kPa) (deg) 1.8

34

Water Surface

Hu Type

B-Bar

Mat. Weight Causes Excess Pore Pressure

Water Surface

Constant

0.3

Yes

-20

SOIL 1

-20

0

20

40

60

80

100

120

140

Project

SLIDE - An Interactive Slope Stability Program

125

1

2

3

4

0

Mag. Susc. SI (x10-6)

Mag. Susc. ln((cgs+2.1)/2) 0

50

10

5

10 20 30 40 AD 1840 (210Pb)

e DetritusGyttja Gyttja FineFinDetritus Clay

Coring Disturbance

Abundant AbundantMacros Macros

600 (550-660) 1150 (1060-1190)

LOI (% organics)

100

Upper 7 cm 0 bagged

0

400

0

2

4

10

6

1

1330 (1300-1370)

2120 (2000–2160) CT scan

200

0

Loop Mag. SI x10

10 2

4

60

0.28

0.28

6

8

10

8

12

16

Safety Factor 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00+

10

100

0

125

250

0

0 50

Material Name Color

Cs peak (AD 1964)

Unit Weight (kN/m3)

Sat. Unit Weight (kN/m3)

Strength Type

16

20

Mohr-Coulomb

SOIL 1

100

200

1300 (1260-1350)

10

34

Water Surface

Hu Type

B-Bar

Mat. Weight Causes Excess Pore Pressure

Water Surface

Constant

0

No

100

150 200

Cohesion Phi (kPa) (deg)

RGB image

two pdfs: 575(562-594) or 655(636-669)

CT scan

-20

0

300

Abundant Macros

400

Light and Dark Bands

400

20

40

7250 (7150–7310)

Mazama Ash

Mazama Ash

Light and Dark Bands

Mazama Ash

102

106

500

9010 (8760–9090)

AMS 14C age and 2 range

600 800

600

9870 (9680–10160)

1520 (1280-1830) 700

900 Abundant Sand layers

700 Laminations Some Clay

1800 (1550-2010)

13000 (12860–13170)

1000

600 Abundant Sand layers

800 Laminations

mapped minerogenic layers

7290 (7220-7380) AD 1800

1020 (930-1090)

Some Clay

210

Pb age and

137

Cs peak

Radiocarbon sample position Lake radiocarbon dates are from the original published literature (recalibrated using Calib 5.0.2) other than Triangle Lake dates, which are presented here.

800

5930 (5710-6190)

HR W-19: 800 (700-1000)

60

Scale

8/9/2012, 8:37:41 PM

80

1:679

2.19 m 1375 +/- 35 5.18 m 2635 +/- 30 8.21 m 5170 +/-100

100

Woody debris with some clastic material Medium black and white sand; fewer organics

Woody debris and abundant macrofossils; debris flow deposit?

Background: fine detritus gyttja background sediment 10

100

Magnetic Susceptibility log (SI + 25)

CT scan RGB image

100

120

T7

T8

HRW-07+B+C: 3470 (3280-3640)

T8a T8b T9 4160 (4000-4330)

? ?

T9a 4460 (4290-4620) T9b? 4740 (4570-4910) T10

T10a

T10b HRW-10: 5330 (5210-5430)

T10c HRW-13: 5690 (5570-5810) T10d

T10f 5700 (5560-5830)

T11 T12 5920 (5790-6050)

140

5 degree slope.slim

5930 (5710-6190)

References:

T6

3160 (3020-3320)

T7a

CASC 145 (31PC): 3530 (3360-3710)* 3600 (3440-3760)

T8

CASC 146: 3960 (3780-4130)

2.0m T8a

1.0m

1542

2.0m

2230 (2150-2330)

OREGON

delta

940 1010

3120

8.0m 1520 (1280-1830)

1360 1520 1542

3300

Bradley Lake

1800 (1550-2010)

Bolan Lake

3420 (3360-3480)

4160 4160

EQ!

EQ! 42N

Sanger Lake CALIFORNIA 124W

1180 (1000-1350)

1480 (1310-1620)

1840 (1660-2020)

3586 (3474-3643)

Loop Mag. SI x10-6

10 2

0

4

6

8

10

137 Cs peak (AD 1964)

100

200

400

500

600 (540-660) MnO2 oxides (log ppb)

600

880 (760-980)

102

106

700

1020 (930-1090) 800

1520 (1280-1830) 900

1800 (1550-2010) 1000

CT scan

mapped minerogenic layers

landslide

EQ!

The examples above suggest both: first destabilzation of the lake margin/walls creates a debrite or turbidite, then pulses of finer material enter from the watershed in response to shaking forming linked debrite/turbidite sequnces.

N

Upper Squaw Lake

~ 180 km

3050 (2950-3160)

landslide

44N

126W

6.0m 880 (760-980)

underwater failures

Second

Upper Squaw Lake

Rogue Apron Smith Apron

600 (540-660)

1020 (930-1090)

3660

charcoal/cm3 3

0

3 km

490 (430-570) 1950 (1870-2010) 2117 (1995–2155)

2550

T8b T9

Cs peak (AD 1964)

first

?

46N

250

200 CASC 173+B+C (55KC): T7 3060 (2860-3220)

137

Goldfinger et al., 2011a coarser grainsize gamma density (g/cc) 1.3 1.6

4.0m

T6a

are followed by external sediment pulses.

underwater failures

WASHINGTON

Smith Apron M9907-33TC

10.0m

3880 (3820-3980)

HRW-06+B+C: 2960 (2820-3070)

T7a

sults show slip surfaces on a 5° slope with varying physical properties and seismic accelerations shown in the table below each panel and at upper right respectively. We vary cohesion (surficial shear strength) from 1.8-10.0 kPa to span a range of expected values for lake sediments from the literature. Horizontal and vertical seismic accelerations are adjusted to reduce the factor of safety to failure (<1.0). Minimum factor of safety slip surface is shown, with associated value. Square plot above each panel is a map of the poles of rotation of the slip surfaces in each model.

The lakes we are investigating are located 100-150 km distance from the nearest hypothetical epicenter on the Cascadia Subduction Zone. Will failures occur? Ground motion predictions at this range are 1.7 to 1.0g respectively (Atkinson and Boore, 2003, 2008) for an Mw = 8.5 earthquake. Actual measurements of ground motions during the 2011 Mw 9.0 Tohoku earthquake exceeded 1.0g at similar ranges (Furamura et al., 2011).

T5b T5c

Point Mag. SI x10-6

0

40

300

Careful examination of some of the deposits from the Sanger Lake 2010 core and preliminary observations from a new core from Muslatt Lake (above) provide clues to the sediment source. In both cores, a coarse layer that includes plant macrofossils is present at the base of the sequence followed by one or more fining upward sequences. The Sanger Lake deposit is comprised of two well-sorted upward fining sequences that are capped by a fine silty clay layer with mean grain size less than background. In contrast, the Muslatt Lake core has a base comprised of unsorted sediment comprised of plant macrofossils and minerogenic material of mixed grain sizes. This layer abruptly transitions to a finer, lightcolored, mineral-rich layer. This sequence is tentatively interpreted to represent an initial debris flow comprised of lake margin detritus followed by the introduction of finer mineral material from the watershed. The example shown above from the Sanger Lake core appears to be two turbidites, which corroborates the findings of Nelson et al. (2006) of tsunami deposits in Bradley Lake at a similar time period (~1500 YBP). The original Sanger core (shown at far left) has a coarse macrofossil and minerogfenic layer at its base much like at Muslatt Lake. The differences in these two Sanger Lake cores is likely a result of core siting, as the original core was taken from the deepest part of the lake and the short core SL2010 was taken at a local minimum near the base of a steep slope at the eastern edge of the lake.

N increasing minerogenic sediment magnetic susceptibility SI (x 10-6) 8 2

1150 (1060-1190)

1360 1520

0

400

10

abundant plant macrofossils just below color and density change

Larger percent clastics; fining upward. Sliver of fine silt/clay at top

48N

T6a

2760 (2720-2790)

Company File Name

1.0m T5a

2320 (2190-2470) CASC 187 (30PC): 2560 (2490-2710) 2730 (2590-2880)

600 (550-660) 100

T4a

2020 (1850-2180)

3890 (3720-4080)

2550 (2410-2720)

T12a

Explanation 2760 (2720-2790)

700

8980 (8770-9090) 500

MnO2 oxides (log ppb)

600

880 (760-980)

500

T3

T6

SLIDE - An Interactive Slope Stability Program

Drawn By

600 (540-660) Mazama Ash

Abundant Macros

7040 (6930-7160) 7850 (7750-7940) 8100 (8020-8180)

940 1010

T5

Analysis Description

Date

20

Pollen conc.

125

LOI (% organics)

Abrupt increase in particle size at base, then fining upward; medium woody debris mixed into the medium sand in lower half; capped with silt/clay

Colombaroli and Gavin, 2010

0.0m

304 (272–465)

T3a

T5c

Project

SLIDEINTERPRET 6.018

T2a

T3

1470 (1330-1620)

300

400

50

Background: fine detritus gyttja

event deposits?

Upper Squaw Lake, OR

0.0m

T4

1060 (950-1180)

400

500

550 (430-670)

Briles et al., 2005, 2008 magnetic susceptibility ln(emu*106) Sanger Lake, CA 0 6 Briles et al., 2008 0 increasing minerogenic sediment magnetic susceptibility ln(cgs) 0 4

250

CASC 141B (30PC): 1590 (1420-1750) 1760 (1580-1930)

T3a

4610 (4520–4740)

5810 (5710-5900) 5910 (5880-5950)

9820 (9630-9950) 10690 (10580-10790) 10950 (10780-11040) 11600 (11390-11810) 12360 (12110-12420) 13310 (13190-13440) 13880 (13780-13990)

0.93

W

gray scale from CT

137

100

300

300

3420 (3360-3480) 3880 (3820-3980)

7360 (7290-7420)

5 degree slope.slim

Density

SI (log axis)

(low resolution)

3600 (3470–3640)

Medium Detritus Gyttja

Company File Name

40

charcoal/cm3 3

-6

Medium Detritus Gyttja

200

3050 (2950-3160)

1:672

(no pore water effects or loading - most stable)

unpublished data

40 0

0

Scale

8/9/2012, 8:37:41 PM

C. high cohesion

ML-K12 Briles, Kelsey and Morey,

Point Mag. SI x10-6 LOI (% organics)

100

1950 (1870-2010) 2230 (2150-2330)

0

LOI (% organics)

300 (270–470)

Drawn By Date SLIDEINTERPRET 6.018

0

Pollen conc.

200

Mag. Susc. ln(emu*50)

100

100

Kusler (unpublished MS thesis)

20

charcoal/cm2

0

influenced by land clearance

LOI (% organics) 0

Colombaroli and Gavin, 2010 % Biogenic Si

Density

Analysis Description

Muslatt L. CA

20

BL-99A Briles et al., 2008

(near inflow) gray scale from CT

250

Triangle L., OR

0

SL2010 Morey et al., 2012

(deepest part of lake)

Upper Squaw L., OR

not scanned

SL 2005? Briles et al., 2008

Bolan L., OR

-20

Sanger L., CA

Slope Stability Analysis", http://www.rocscience.com; Toronto, Canada: retrieved Aug. 10, 2012). Re-

T1 T2

CASC 170 (55KC): 1200 (1100-1290) 1370 (1260-1500)

T5b

The three panels to the left summarize results from slope stability output from the program SLIDE (("SLIDE 6.0 – 2D Limit Equilibrium

250 (200-300) CASC 168 (55KC): 490 (380-590)

CASC 160 (55KC): 740 (680-810) 1070 (970-1200)

HRW-24: 300 (230-410)

T4 T4a 1210 (1100-1340)

1300 (1260-1350)

Rogue Apron TN0909-01TC

Goldfinger et al., 2011a coarser grainsize magnetic susceptibility SI (x10-6) 0 80 0.0m

T2a

T1 T2

1650 (1490-1810)

0.15

Sanger Lake, CA: Sanger Lake is a spring fed cirque lake (1550 m elevation) with a small drainage.

` ` ^ `^ ^ California

!

M.S. ( S.I.) 0 400

?

0.15

W

-20

Bolan Upper Squaw Lake Lake ! Muslatt ! !! Lake Lagoon Creek ! E ! Sanger # * # Smith * Lake

(

# *

RR0207-56PC-TC

T5a 0.94

40

M9907-31PC/TC

Hemipelagic age and estimated 2 range

250 Bradley Lake ages

T5

A. high cohesion

0

#* * #

(

TN0909-01PC/TC

Exploratory results suggest that accelerations of 0.28g or less are required to destabilize shallow slopes in these lakes.

!

!

% Biogenic Si

CT density

(grayscale trace through CT)

50 100 150 200 250 300 350

The Upper Squaw Lake core (right) also provides clues to sediment source. Magnetic susceptibility and charcoal concentration appear correlated, with high concentrations of charcoal throughout deposits interpreted as instantaneously deposited. The source of this charcoal is most likely from outside the lake, as any redistributed charcoal would not be consistently high scenario reflects the source of thesequence. disturbance Destabilization of sediments within the lake throughoutWhich a rapidly deposited

Bolan Lake, OR

Sample # AMS 14C age and 2 range

7290 (7220-7380)

Lake radiocarbon dates are recalibrated using Calib 5.0 from the original data.

CSZ

(

!!

E

Alsea Bay E

TRI-1

Slope Stability Analysis

Effingham and Saanich Inlets: Not technically lakes, but rather fjords on Vancouver Island, British Columbia, Canada with submarine debris flow deposits that have been interpreted to be earthquake-triggered, and the timing of these events suggest they are a result of local and subduction zone events. Events show features similar to marine turbidite deposits, with coarse bases fining upward. Radiocarbon dating of shells and plant material, varve counting and datums (including the Mazama Ash) are used for age control.

!

Nestucca E

# Hydrate Ridge *

H

100 10 200 100 0 Gray M . S . ( S . I . ) 210Pb(excess) Level

Fjords !

!

8.0m T26 (11750-12050)

Explanation 7290 (7220-7380)

marine cores: best ages within site

MARINE

1.8 g/cc 1.0

46°0'0"N !

! !

Netarts Bay E

Salmon River

CASC 157: 11870

!

! !

E

Triangle Lake/ Hydrate Ridge Basin West

Abundant Sand layers

H

T24 (11290-11730) T25 (11180-11600)

~ 520 km

!

E

!

Stanley Lake E Ecola Creek E Rockaway Beach

Siletz River E

RR0207-56PC

Pb)

600

H

(10790-11280) T23

CASC 156: 11400

60

(

Columbia River E Columbia River

# *

210

Laminations

H

H

40

(

# *

# * # * # #* #* * # *

!

E Willapa Bay E Grayland Plain E Long Beach E Willapa Spit

Correlation Examples

Abundant Sand layers

10950 (10780-11040)

H

6.0

T19 (10180-10340) T19a (10130-10390)

CASC 155: 11530

Coseismic Subsidence and Tsunami Sands: Rapid coseismic subsidence followed by inundation and subsequent burial of coastal lowlands with tsunami-transported sand result in stratigraphic sequences of great earthquakes. These records represent hundreds to thousands of years, but rarely span more than 5,000 years. Correlation of coastal events is mainly dependent on age control, as other correlation methods are not presently known. Marine and coastal records show many similarities, however the differences between dates at onshore sites are great enough in many cases that many onshore events cannot be reliably correlated on the basis of 14C ages alone, which is problematic even with precise data.

Lake Washington

!! !

Copalis River E Grays Harbor Johns River EE

# *

AD 1950 (

Some Clay

H

H

48°0'0"N

(

# *

# #* *

500

!

# *

# *

H

10690 (10580-10790)

!

# * # *

Could the disturbance event deposits be a result of other mechanisms?

7850 (7750-7940)

H

5.0

T16 T16a

20

(

# * # *

E

Light and Dark Bands

H

(8150-8350) T15 T15a

8850 (8660-8990)

0

(

E

Uclulet E

Effingham Inlet Saanich Inlet

Mazama Ash 400

8980 (8770-9090)

Turbidite Paleoseismology: Earthquake-triggered turbid flows transport coarser sediment from shallower water to the abyssal plain. The deposits are recognized as coarser, fining upward deposits as compared to the background hemipelagic sediment. Physical properties (grain-size proxies) through these deposits show distinctive excursions which, along with supporting radiocarbon ages, are correlated along-strike across distances that can be only explained as a result of earthquake-triggering from a subduction zone great earthquake. Most of the cores contain the Mazama Ash datum and typically contain stratigraphic records spanning much or all of the Holocene. Radiocarbon dates from planktonic foraminifers are corrected for the age of the water in which they lived (reservoir age). Marine sites are shown as triangles.

E

Port Alberni

7360 (7290-7420)

T12a

9070 (8910-9230) CASC 149: 9150

E E

Mazama Ash

H

T11 T12

6630 (6440-6810)

E

Kakawis Lake Tofino

Are disturbance events correlated over large enough distances to infer seismic triggering?

5810 (5710-5900) 5910 (5880-5950)

5850 (5700-5990) 4.0m

60

Kanim Lake

0

Correlations are in progress and ongoing. Small inland lakes at a distance of 100 km from the coast (~180 km from the deformation front) have deposits that correlate to marine seismogenic turbidites. We now have collected cores along a transect from 20 km from the coast to ~100 km. These cores show disturbance event deposits change with distance from the coast and lake characteristics. We have found that: - Disturbance event deposits are most likely to be obvious, correlatable units and record a wider range of earthquakes if they are from sites with high external sediment input (i.e. landslidedammed lakes such as Upper Squaw Lake). These sites, however, also record other events such as from floods and fire and produce a more complicated sedimentary record. - Although a large supply of sediment is needed for seismic shaking to produce obvious deposits, spring-fed cirque lakes such as Bolan Lake have thin layers that can be recognized in the magnetic susceptibility. The use of CT scans and high-resolution physical properties could significantly improve stratigraphic interpretation. - Small lakes, even those with a limited sediment source, record earthquakes if they are in close proximity to shaking (Sanger and Muslatt Lakes). - In all cases, the best records of disturbance event deposits come from the deepest part of the lake. Triangle Lake and Sanger Lake core SL2010 do not have the detail, range in particle size, and expanded deposits seen at some of the other sites.

Atkinson, G. M. and D. M. Boore: Empirical ground-motion relations for subduction zone earthquakes and their application to Cascadia and other regions, Bull. Seism. Soc. Am. 93, 1703—1729, 2003. Atkinson, G. M. and D. M. Boore: Erratum: Empirical ground-motion relations for subduction zone earthquakes and their application to Cascadia and other regions, Bull. Seism. Soc. Am. 98, 25672569, 2008. Colombaroli, D. and D. G. Gavin, 2010, Highly episodic fire and erosion regime over the past 2,000 y in the Siskiyou Mountains, Oregon, PNAS 107 (44), 18909–18914. Furumura, T., Takemura, S., Noguchi, S., Takemoto, T., Maeda, T., Iwai, K., and Padhy, S., 2011, Strong ground motions from the 2011 off-the Pacific-Coast-of-Tohoku, Japan (Mw=9.0) earthquake obtained from a dense nationwide seismic network: Landslides, v. 8, p. 333–338.

EQ!

Could the disturbance event deposits be a result of fires? Colombaroli and Gavin (2010) show that in Upper Squaw Lake sediments, charcoal concentration peaks lead minerogenic events suggesting erosion following fire, however the data are not consistent. The high concentration of charcoal throughout the deposit confirms the minerogenic deposits come from an external source (see above), a conclusion supported by the historic portion of the core (where high magnetics are also associated with high charcoal concentrations). Preliminary geochemical analyses were run on six samples from the thickest deposit in the sequence at right. Results reveal the presence of an oxidation profile supporting relatively instantaneous deposition, however the entire deposit was not sampled throughout (work in-progress).

low res mag

106

3420 (3360-3480)

4850 (4620-5030) 3.0m T10 5050 (4880-5250)

CASC 72: 8250

RGB image

Colombaroli and Gavin, 2010 Muslatt Lake

Sanger Lake (SL2010) Mean Grain Size

CT scan

Would shaking from a great earthquake be strong enough to destabilize lake sediment?

H

influenced n by logging

T9 T9a

CASC 31:

Relevant Paleoseismic Archives

Kilometers 200

150

Are They a Result of Earthquakes?

3050 (2950-3160)

2.0

CASC 146:

20

(

100

Upper Squaw L., OR

Coarse layers containing plant macrofossils precede the more visible minerogenic layers.

T8b

3960 (3550-3830) 4320 (4140-4510) 4540 (4360-4730)

low res loop mag

earthquakes.

Is the sediment source of internal to the lake?

114

T6 T6a

CASC 173+B+C:

0.00001

112

CASC 187+B:

2560 (2490-2710) 2730 (2590-2880) 2820 (2680-2990)

T7a 3060 (2860-3220) 3160 (3020-3320) 2.0m

0.000008

110

2020 (1850-2180) 2320 (2180-2470)

0.000006

108

T5a

0.000004

106

CASC 141B: 1590 (1420-1750) 1760 (1580-1930)

1150 (1060-1190)

H

0.000002

Long-distance stratigraphic correlation of marine turbidite deposits among widely-spaced sites has been used to infer synchronous deposition, and if the spatial extent exceeds that which is reasonable for other mechanisms, then earthquake triggering is likely. Correlation of lake disturbance event deposits between lake cores and between lake and marine cores is ongoing. Preliminary correlations support long-distance correlations between lake and marine cores. Long-distance correlation between sedimentary records from such different depositional environments supports that these events are earthquake-triggered. The interpretation that they are earthquake-generated deposits is supported by research in eastern Canada, Lake Lucerne, Dead Sea, Lake Biwa, Chile and elsewhere.

T4a T5

8460 (8270-8600)

50

5

104

T4

CASC 170:

Location Map and Available Data 25

4

600 (550-660)

H

7040 (6930-7160)

0

3

Dark

1230 (1180-1300) 1370 (1270-1500)

Similarities between physical property characteristics and timing of marine and lake deposits supports the interpretation that they are seismogenic. Remarkable similarities between thick disturbance event deposits of similar timing from Upper Squaw Lake and Smith Apron (M9907-33TC) cores are visible in great detail using the CT data. Proximal lake disturbance event deposits (such as those from Sanger and Muslatt Lakes) differ from marine deposits by the presence of a coarse organic macrofossil and terrigenous layer (tentatively interpreted as debrites), abruptly followed by single or multiple pulses of finer mineral material with normal grading. The finer mineral is comprised of silty clay, and is now interpreted as having a source external to the lake because of the presence of high concentrations of charcoal throughout, and low concentrations of biogenic silica (although data were acquired at a much lower resolution). If deposits record a crude primary signal of shaking (“paleoseismogram”), the source is likely a pulse of sediment-rich water from within the watershed. Simple limit equilibrium calculations of slope stability (pseudostatic) suggest expected PGA for these inland sites is likely sufficient to trigger sediment failures within the lakes from subduction earthquakes with Mw lower than 8.0.

CatalaE Lake

2

AD 1950 (210Pb)

102

T3 T3a

1.0m

E

1

The relationship between magnetic susceptibility and the amount of organic material (LOI) in Bolan Lake is shown at left.

Magnetic Susceptibility (emu)

ln((cgs+2.1)/2)

0

0

H CASC 160:

740 (680-810) 1070 (970-1200)

Bolan Lake, CA

0

Mag. Susc.

LOI (% organics)

0 150 300

Gamma density 0.0m

50 45 40 35 30 25 20 15 10 5 0

high res. point mag

density (loop)

gamma density

not scanned

Sanger L., CA

Increased post-forest fire erosion Unusual meltwater events Storms/Floods post-settlement land clearance and logging

MARINE LAKE Why would earthquake-triggered marine and lake deposits look so similar when their “waterSmith Apron Upper Squaw sheds” and depositional environments are so different? Correlated lake-marine sequences M9907-33TC Lake, OR suggest that in many cases, the similarities are primarily a function of the deposit structure (example shown at right). Details evident in the CT scans of the massive deposit to the right is even more compelling. The complicated sequences that comprise the surrounding structure in the Upper Squaw Lake core (shown to the right next to an a likely correlative deposit in marine core M9907-33TC) suggest complexity at that site that is either not present in marine core 33TC, or is very subtle. The large watershed (40 km2) relative to basin size (0.072 The similarities between marine core M9907km2), and high relief (maximum elevation within drainage is ~1.7 km), ensures that Squaw 33TC and the lake core from Upper Squaw Lake support the interpretation of earthquake trigCreek (which feeds the lake) has a large and variable sediment load, and the sedimentary gering. The stratigraphic complexity in Upper record must therefore be influenced by floods and post-fire erosion. Squaw Lake suggests it records more than

MnO2 oxides (log ppb)

high res mag (see note)

charcoal concentration

102

Rogue Apron M9907-31PC/TC Goldfinger et al., 2012

Layers high in mineral content have also been attributed to other causes, such as -

LAKE

Much more detail can be seen in the CT scan (left) of the core as compared to the line-scan RGB imagery (right). The mineral-rich layers are frequently the most obvious features in the core, and the full extent of the disturbance event deposit may not be recognized.

Stratigraphic resolution and complexity

influenced by land clearance

MARINE

Disturbance event deposits in these lake sediments were originally observed as layers with high mineral and low organic content as compared to background sediment. Excursions in the physical property data (magnetic susceptibility and density) reflect these variations in mineral content, although they are also affected by particle size and composition (note Mazama Ash peaks in magnetic susceptibility data for Sanger and Bolan cores). The larger percentage and variability in organic content in these cores must be taken into consideration when comparing marine and lake physical property data. High resolution 3-D Computed Tomography (CT) scans of sediment cores reveal less-visible layers and illuminates sedimentary structures which aids in the identification and interpretation of disturbance event deposits.

sequence 2

Observations that disturbance event deposits in Cascadia inland lake sediments have similarities in timing and some characteristics as compared to marine seismogenic turbidite deposits prompted this investigation into the possibility that these deposits were formed as a result of shaking during great earthquakes.

The disturbance event deposits we have investigated differ as a result of the type and availability of sediment, size of lake, drainage area, terrain near the lake shore, location of core with respect to lake bathymetry, and distance from the coast. Compared to background sedimentation, the disturbance event deposits are coarsergrained, have a higher percentage of mineral content, include fining-upward components, and may have a coarser organic layer at the base of the sequence. Physical property (magnetic susceptibility, gamma and Computed Tomography (CT) density) and particle size data through the disturbance event deposits investigated show similarities to deposits of similar age in the marine turbidite record, except where the concentration of organic matter attenuates the signal. Geochemical analyses through one disturbance event deposit (occurring between units dated at 880 (760-980) and 1020 (930-1090) BP) from the Upper Squaw Lake core revealed a manganese oxide profile from the downward oxidation indicative of a unit deposited rapidly.

Preliminary Interpretations

What Are These Disturbance Event Deposits?

Initial Observations

sequence 1

Lake Data

Lacustrine sedimentary sequences have been successfully used to develop earthquake chronologies and seismic hazard assessments in a variety of settings, however most of these lakes are large (> 10 km2), deep, and in close proximity to an active fault. The recent discovery of disturbance event deposits in small (0.04 - 1.20 km2) southern Cascadia inland lakes with similar characteristics and timing as compared to marine seismogenic turbidites prompted us to investigate the nature of these deposits and compare to the marine record. For this study we investigated lake records from four lakes from the Klamath Mountains of northern California and southern Oregon: Sanger, Bolan and Muslatt Lakes (predominantly spring-fed, cirque lakes with small watersheds), and Upper Squaw Lake (a stream-fed, landslide-dammed lake with a large watershed), and Triangle Lake from the central Oregon Coast Range 43 km from the coast.

Loss on Ignition (LOI; % organics)

Abstract

This core was acquired using overlapping drives; the high res mag susc and CT here are from a different section as the charcoal and low res mag susc.

Or extreme floods? Muslatt Lake Density 0 0

50

100

150

CT scan

gray scale from CT 125 250

Lake Washington sediments were evaluated for flood deposits using historical records (Karlin et al., 2004). The authors argue that seismogenic turbidites are not likely to be confused with stormgenerated deposits because even the most severe historical (post-1916) storm deposits represented in Lake Washington are very thin (~ 0.5 mm) discontinuous stringers of clay with no magnetic susceptibility signature present only near the mouth of the river. Additional evidence comes from Muslatt Lake core (left). CT scans of this core show there is little structure in this core above the large sequence from 80-160 cm over the past 600+ years. During this time there must have been multple 100-year storms.

base of core ~600 YBP

Future Work

- Continue to work on correlations between inland lakes sedimentary records and marine seismogenic turbidites. - Complete MnO2 profile through Upper Squaw Lake deposit and others (both marine and lake environments), that appear to be instantaneously deposited. - More detailed descriptions and analyses are needed on all cores. - Look at relationships between size of deposit and distance from coast. Find a lake site that is far enough away from the subduction zone, and without local faulting, to use as a comparison (no shaking).

See Black et al. poster “STRATIGRAPHIC CORRELATION OF SOUTHERN CASCADIA TURBIDITES VIA PAIRING OF SUB BOTTOM PROFILES AND SEDIMENT CORE DATA”: T23E-2736

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