Potential Lacustrine Records of Cascadia Great EarthquakesAnn E. Morey1, Chris Goldfinger1, Christy E. Briles2, Daniel G. Gavin3, Daniele Colombaroli4

and Jennifer E. Kusler3

Lacustrine sediments have been used successfully over the past few decades to develop earthquake chronologies and rupture assessments in a variety of locations and settings, from large lakes in Japan and Chile to Alpine lakes in central Europe. Although inland lakes in the Pacific Northwest have been used extensively for fire and vegetation reconstructions, they have been largely ignored with respect to their tectonic setting. Strong shaking from great earthquakes at subduction zones is known to produce significant environmental disturbance and can result in lake deposits that are distinctive and datable records of these events. Cascadia paleoseismic studies, including those at Lake Washington, Bradley Lake, and Effingham and Saanich Inlets, provide direct evidence that records of Cascadia great earthquakes are preserved in a variety of sedimentary archives.

The field of marine turbidite paleoseismology has resulted in advancements which we have now begun to apply to inland lacustrine sediments using the records at Sanger and Bolan Lakes (both spring-fed, cirque lakes), and Upper Squaw Lake (a stream-fed, landslide-dammed lake) located 45-100 km inland from the coast near the California/Oregon border. Inorganic terrigenous layers are visible in these sediments, and physical property data (via CT scans, magnetic susceptibility and gamma density) show characteristics that correlate between lakes, and more surprisingly, correlate great distances to seismogenic offshore turbidite deposits.

The highest resolution site is Upper Squaw Lake, a 7.2 ha landslide-dammed lake which drains a 40 km2 watershed. A 10 m core spanning the past 2,000 years was extracted from this site, and is comprised of silty gyttja interbedded with inorganic turbidite deposits. Six major events are observed this core, similar to the number of events in the marine turbidite record in the same time period, with supporting age control. The characteristics of the physical property data are remarkably similar to those found at the Smith Apron offshore site approximately 160 km away. Striking correlation examples include a multiple peaked event or events at ~1500 years before present (ybp), a single peak fining upward with a small excursion near the top of the sequence at ~1000 ybp, and a large single peak for an event poorly constrained at ~500 ybp. The number of observed events is also somewhat comparable to those found at the Oregon coastal site Bradley Lake which records tsunami inundation, especially if multi-peaked sequences at Upper Squaw Lake represent multiple events as suggested by the clusters of disturbance events from a similar time at Bradley Lake.

The great distance and multiple depositional environments over which these events correlate suggests these are earthquake-generated deposits and supports the hypothesis that gravity-driven seismogenic sediment deposits may record a crude primary signal of shaking which we call a “paleoseismogram”. We hope to expand this investigation, by increasing the number of inland sites to be used in conjunction with marine and coastal records, to refine Cascadia paleo-rupture models by improving estimates of along-strike segmentation and the down-dip extent of the locked zone.

ABSTRACT

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.

DEEP-SEA, COASTAL and INLAND LAKE SITES

COMPARISON OF MARINE AND LACUSTRINE RECORDS

46N

126W

2

Goldfinger et al., 2011a

1.3 1.6

Smith ApronM9907-33TC

gamma density (g/cc)

~ 520 km

42N

10.0m

6.0m

8.0m

0.0m

2.0m

4.0m

8

Upper Squaw Lake, OR

magnetic susceptibilitySI (x 10-6)

Colombaroli and Gavin, 2010

1.0m

48N

coarser grainsize

increasing minerogenic sediment

SmithApron

124W

N

137Cs peak(AD 1964) CSZ

44N

BradleyLake

influ

ence

dby

logg

ing

CASC 146: 3960 (3780-4130)

CASC 168 (55KC): 490 (380-590)

550 (430-670)

1070 (970-1200)

1370 (1260-1500)

1760 (1580-1930)

2020 (1850-2180)

2730 (2590-2880)

3890 (3720-4080)

2320 (2190-2470)

3160 (3020-3320)

3600 (3440-3760)

250 (200-300)

CASC 170 (55KC): 1200 (1100-1290)

CASC 160 (55KC): 740 (680-810)

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

CASC 187 (30PC): 2560 (2490-2710)

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

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

T4

T5

T6

T7

T8

T9

T3

T5a

T5b

T7a

T6a

T8a

T8b

T4a

T3a

T5c

T1T2

T2a

0 4

0.0m

1.0m

Sanger Lake, CA

magnetic susceptibilityln(cgs)

Briles et al., 2008increasing minerogenic sediment

Goldfinger et al., 2011a

0 80

Rogue ApronTN0909-01TC

magnetic susceptibilitySI (x10-6)

coarser grainsize

RogueApron

Sanger Lake

0.0m

1.0m

2.0m

OREGON

WASHINGTON

CALIFORNIA

UpperSquawLake

~ 180 km

POSSIBLE MECHANISMS

USEFULNESS OF EARTHQUAKE RECORDS FROM CASCADIA INLAND LAKESWe are interested in lacustrine sedimentary archives for many reasons:

Identifying the inland extent of the locked zone and segmentation. With the past occurrence of great earthquakes in Casca-dia now well established, attention has turned to magnitude, recurrence intervals, the meaning of ETS (episodic tremor and slip), and segmentation of the margin. The downdip extent and segmentation in Cascadia are both controversial. Downdip extent is somewhat constrained by thermal and GPS models, as is subsidence along the coast. We expect to improve our un-derstanding of the spatial expression of Cascadia earthquakes using lacustrine archives to address the down-dip extent of the locked zone, segmentation towards improving our understanding of the hazards to populated areas.

Confirmation of fine-grained turbidites. Recently, the identification of small muddy turbidites in deep-sea sediment cores has suggested more frequent earthquakes in southern Cascadia. The significance of this is substantial as it increases the chance of southern Cascadia events (Goldfinger et al., 2011a). Stratigraphic records from lakes with high sediment input, such as the landslide-dammed Upper Squaw Lake in southern Oregon, appear to be highly sensitive recorders of earth-quakes and silty layers easily recognizable against the more organic-rich background sedimentation (see panel at right).

Event age comparison and reservoir age. Well-placed radiocarbon dates from events in lake cores can be compared to cor-relative dates in marine cores and coastal datasets to hopefully understand, and possibly correct for, biases in each set. Care-fully chosen sample material and placement should provide dates that are accurate and free of the spatially- and time-varying reservoir effect which affect marine radiocarbon dates from planktonic foraminifers.

FUTURE WORK

Sanger Lake, CA: A massive slide of unknown age berms the eastern side of the lake which we speculate may harbor sediment which is released during an earthquake to produce the large excursions in magnetic susceptibility (above). The entire record spands the Holocene; only the last 4000 yrs are shown here.

Bolan Lake, OR: Although there are no visible silt or clay layers in this core, there is variability in the magnetic data that matches that from the Sanger Lake core. Core spans the Holocene; only the last 4000 yrs are shown here.

Upper Squaw Lake, OR: The magnetic susceptibility record from this 2000 yrs record shows a remarkable similarity to the density record from the Smith Apron site. Alternating gray and white shading in bar to left of magnetics show visibly recognizable silt layers in the core (gray).

Bradley Lake, OR: Disturbance event dates are included for comparison (dates in red: re-analyzed as published in Goldfinger et al., 2011a).

UpperSquaw

Lake

3 km

N

BolanLake

Explanation

Sample # AMS 14C age and 2 range7290 (7220-7380)

Hemipelagic age and estimated 2 range7290 (7220-7380)

020406080100120140

04080120

1.0

CASC 276: 490 (420-550)*

M9907-34 TCKlamath Channel1.6

T1

T2

T3

T2a

0

10

20

30

40

50

60 H

H

M9907-30-31TCTN0909-01TCRogue Apron

1.21.5

RR0207-55KCRogue Apron

0 60

550(430-670)

850(740-970)

70

*

sample void

3678

250 (200-300)

210Pb (excess)

H

H

H

CASC 168: 480 (380-590)

CASC 160:740 (680-810)

30TC 31TC

600(510-700)

H

H

H

HT1

T2

T3

T2a

T4

T3a70

80

90

H

T4

T5

01TC

1140 (1030-1250)

1510(1390-1640)

-30

CASC 168 490 (380-590)

1070(970-1200)

250 (200-300)

CASC 170 1200 (1100-1290)

CASC 160740 (680-810)

sample void

1.3

14501650

14501650

Hemipelagic clay

Turbidite silty mud

Sand

Silt

Mottled clay

Burrows

Very fine sand

Lithology

Samp. #: Erosion corr. 14C age & 2 rangeCASC 11: 7298 (7220-7377)Gamma Density (g/cm3)

Radiocarbon sample location

Explanation

Correlation Lines, dashed if uncert.

High-resolution mag. susc. (SI)

CT density (gray level)

Sample #: 14C age & 2 rangeCASC 11: 7298 (7220-7377)

Hemipelagic age & est. 2 range7298 (7220-7377)

P-wave velocity (m/s)

1020 (930-1090)

600 (540-660)

880 (760-980)

1020 (930-1090)

600 (540-660)

880 (760-980)

Paleoseismogram. Why would characteristics between marine turbidites and inland lacustrine turbidites look so similar? Our current working hypothesis is that the patterns we are correlating are related to the earthquake, the only thing these sites have in common. How? We suspect that the signatures represent unique energy signatures of the source mechanism, a “paleoseismogram”. Multiple subev-ent ruptures, common for great earthquakes, may leave such a signature. Experi-mental results support this hypothesis.

The results of an experiment (left) shows deposition of a bimodal grain size sedi-ment following “triggering” by an external pump simulating an earthquake’. It pro-duced a debrite, cousin to a turbidite, with fining upward pulses that reflect the input signal.

Rogue Apron cores (shown here, along with a core from Klamath channel) show small excursions in physical properties, comprised of slightly denser (coarser-grained), darker sediment that we infer are muddy turbidites repre-senting smaller southern Cascadia events (indicated by an “a” after the event number). The green traces and numbers represent the (tentative) correlative section of the Upper Squaw Lake magnetic susceptibility record and radio-carbon dates.

REFERENCES

Briles, C.E., C. Whitlock, P.J. Bartlein, P. Higuera, 2008, Regional and local controls on postglacial vegetation and fire in the Siskiyou Mountains, northern California, USA, Palaeogeography, Palaeoclimatology, Palaeoecology 265 (2008) 159–169Briles, C.E. C. Whitlock, Briles, C., Whitlock, C., Bartlein, P.J., 2005. Postglacial vegetation, fire and climate history of the Siskiyou Mountains, Oregon, USA. Quaternary Research 64, 44–56.Chlieh, M., Avouac, J.-P., Hjorleifsdottir, V., Song, T.-R.A., Ji, C., Sieh, K., Sladen, A., Hebert, H., Prawirodirdjo, L., Bock, Y., and Galetzka, J., 2007, Coseismic Slip and Afterslip of the Great (Mw9.15) Sumatra-Andaman Earthquake of 2004: Bulletin of the Seismological Society of America v. 97, p. S152-S173.Doig, R., 1986, A method for determining the frequency of large-magnitude earthquakes using lake sediments, Canadian Journal of Earth Sciences, 1986, 23:(7) 930-937Doig, R., 1991, Effects of strong seismic shaking in lake sediments, and earthquake recurrence interval, Témiscaming, Quebec, Canadian Journal of Earth Sciences, 1991, 28:(9) 1349-1352Goldfinger, C. and others, 2011a in press, Turbidite event history: Methods and implications for Holocene Paleoseismicity of the Cascadia subduction zone: U.S. Geological Survey Professional Paper 1661-F.Goldfinger, C., 2011b, Possible turbidite record of earthquake source characteristics: a small scale test, NEHRP Annual Report, Volume 34: Reston, VA, U.S. Geological Survey, p. 18.Goldfinger, C., Morey, A., Black, B., and Patton, J., 2011c submitted, Spatially Limited Mud Turbidites on the Cascadia Margin: Segmented Earthquake Ruptures?, in Pantosti, D., Gracia, E., Lamarche, G., Nelson, C.H., and Tinti, S., eds., Research Conference Submarine Paleoseismology: The Offshore Search of Large Holocene Earthquakes: Obergurgl, Austria, Natural Hazards and Earth System Sciences.Karlin, R.E., Holmes, M., Abella, S.E.B., and Sylwester, R., 2004, Holocene landslides and a 3500-year record of Pacific Northwest earthquakes from sediments in Lake Washington: Geological Society of America Bulletin, v. 116, p. 94-108.Kelsey, H.M., Nelson, A.R., Hemphill-Haley, E., and Witter, R.C., 2005, Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone: GSA Bulletin, v. 117, p. 1009-1032.Patton, J.R., C. Goldfinger, A.E. Morey, K. Ikehara, C. Romsos, Y. Djadjadihardja, U. Udrekh, 2012 (submitted), A 7,500 year earthquake history in the region of the 2004 Sumatra-Andaman Earthquake, Earth and Planetary Science LettersSchnellmann, M., Anselmetti, F.S., Giardini, D., and Ward, S.N., 2002, Prehistoric earthquake history revealed by lacustrine slump deposits: Geology, v. 30, p. 1131-1134.

Acknowledgements: Funding has been provided by NSF Awards EAR 9803081, EAR-0001074, EAR-0107120, EAR-0440427 and OCE-0550843 (reservoir model development) and OCE 0850931 (2009 cruise). The U.S. Geological Survey substantially supported the work through Cooperative Agreements 6-7440-4790, 98HQAG2206, and 99HQAG0192; and The U.S. Geological Survey National Earthquake Hazard Reduction Program grants 02HQGR0019, 03HQGR0037, 06HQGR0149, and 07HQGR0064 to Goldfinger, and 02HQGR0043, 03HQGR0006, and 06HQGR0020 to Nelson. The American Chemical Society awarded support to Ph.D. student Joel Johnson for core collection and analysis at Hydrate Ridge under ACS PRF 37688-AC8.

Briles et al., 2005, 2008

600 (550-660)

1150 (1060-1190)

1950 (1870-2010)

3880 (3820-3980)

3420 (3360-3480)

2230 (2150-2330)

3050 (2950-3160)

0 60

100

200

magnetic susceptibilityln(emu*106)

304(272–465)

2117(1995–2155)

3586(3474-3643)

Bolan Lake, OR

490 (430-570)

1180 (1000-1350)

1840 (1660-2020)

g

1800 (1550-2010)

1520 (1280-1830)

1020 (930-1090)

600 (540-660)

880 (760-980)

250

940

1010

136015201542

2550

3120

3300

3660

41604160

250

940

1010

136015201542

Bradley Lake ages250marine cores: best ages within site

Lake radiocarbon dates are re-calibrated using Calib 5.0 from theoriginal data.

Why would earthquake-generated marine and lacustrine

sedimentary archives look so similar when the depositional

environments are so different?

We suggest that shaking-induced failures in response to the an earth-quake become turbid flows underwater in both environments; differential settling results in fining-upward deposits.

Is the primary source of sediment in these deposits internal or

external to the lake?

- Increase in sediment delivery by rivers to the site of deposition would be slower in response to an earthquake as compared to the instantaneous deposition of sediment internal to the lake, and would likely show reverse, then normal grading, as with flood or hyperpycnal flow deposits.

- There is anecdotal evidence of lake “whitening” immediately after an earthquake (Doig, 1986, 1991), suggesting remo- bilization of sediment within the lake.

- High-resolution CHIRP profiles have been extremely useful for interpretation of sedimentation history and can be used to determine source, with river transported sediments thinning away from the input, and remobilized sediments deposited lake-wide (e.g. Schnellmann et al., 2002, Karlin et al., 2004)

ARE THEY EARTHQUAKE-GENERATED DEPOSITS?

The observation that characteristics in published down-core

physical property data from several Pacific Northwest lake

cores look remarkably similar to characteristics in deep-sea

sediment cores provided incentive to investigate the possibility

that lake archives also record Cascadia earthquakes.

Marine Environments - Synchronous Triggering

Confluence Test. Adams (1990) observed that at Juan de Fuca Canyon, and below the confluence of Willapa, Grays, and Quinault Canyons, cores contain 14–16 turbidites above the Mazama ash. Below the Juan de Fuca and Willapa Chan-nel tributaries, cores in the main Cascadia Channel contain 13 post-Mazama turbidites. Adams (1990) reasoned that these events must have been synchronously triggered be-cause if these events had been independently triggered with more than a few hours separation in time, cores taken below the confluence should contain from 26–31 turbidites, not 13, as observed.

Density (g/cm3)

Radiocarbon sample location

Explanation

Core break

Correlation Lines, dashed if uncertain

High-resolution point magnetics

Sample # AMS 14C age and 2 range

Reversed AMS 14C age and 2 range

CASC 11: 7290 (7220-7380)

CASC 11: 7290 (7220-7380)

H/P Holocene/Pleistocene boundary

Oldest Mazama ash bearing turbidite

Hemipelagic age and estimated 2 range7290 (7220-7380)

Erosion corrected AMS 14C age and 2 rangeCASC 11: 7290 (7220-7380)

Hemipelagic clay

Turbidite silty mud

Sand

Silt

Mottled clay

Burrows

Pleistocene

Very fine sand

ShellWood fragment

Hemipelagicbasal boundary

Correlation details from two pairs of cores on the Cascadia margin are shown in the figure to the left. Panel A: events 8-11 in cores from JDF Channel (left) and Cascadia Channel (right). Note correspondence of size, spacing, number of peaks, trends between events, and form of physical property traces between these cores. Panel B similarly displays events 10-14 in Juan de Fuca Channel (left) and Rogue Channel (right). Physical property data are proxies for grain size. Light blue traces are gamma density, dark blue traces are magnetic susceptibility. Panel A cores are part of the same channel system, distance = 475 km. Panel B cores are in channels that do not meet, distance = 500 km.

H

CASC 107, 2324,140 (4,000–4,290)

CASC 4, 1167,100

(7,000–7,210)

CASC 110, 117 7,580

(7,470–7,690)CASC 109, 234, 1145,760 (5,640–5,830)

CASC 108,113 4,760 (4,630–4890)

A.

1.31.6

Juan de Fuca11/12PC

0 100

Cascadia23/25PC

-10 400 1.31.7 -10 400

B.Juan de Fuca

11/12PCRogue31PC

10001.21.61.21.7

4.0

5.0

4.0

notcorrelated

CASC 108,113 4,760

CASC 109, 234, 1145,760 (5,640–5,830)

(4,630–4,890)

2.0

1.52.0

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

T11

T8

T9

T10

T11

T12

T13

T14

T10 T10f

CASC 131 3,490

(3,310–3,660)

CASC 1324,160

(3,980–4340)

CASC 115 6,440

(6,280–6,570)

CASC 32, 7,100(6,980–7,260)

CASC 9, 7,670(7,530–7,820)

CASC 47 3,500 (3,340–3,680)

6,000(5,870–6,120)

5,850(5,700–5,990)

6,900(6,780–7,030)

T12a

6,630(6,440–6,810)

6,090(5,910–6,290)

5,790(5,630–5,934)

5,790(5,630–5,934)

4,740(4,560–4,930)

Depth(m)

Depth(m)

Depth(m)

Depth(m)

Stratigraphic Correlaton. When turbidite deposits can be correlated among widely spaced sites, synchro-nous deposition can be established or inferred, and if the spatial extent exceeds that which is reasonable for other mechanisms, then earthquake triggering is likely. Below is an example from the margin-wide event correlation published by Goldfinger et al., 2011a.

Lacustrine Environments - previous interpretations of minerogenic layers

Inland lake sediments from sites west of the Cascade Range have been used extensively to reconstruct climate, vegetation and forest fire histories. Silt or clay layers in lake sediments from these studies have been typically interpreted as:

- unusual meltwater events

- increased runoff following severe storms

- post-forest fire erosional events

- effects of land clearance and logging roads

To this list we add . . . - earthquakes

. . . based on the work in Lake Washington.

Historical data at Upper Squaw Lake show that land clearance can have a significant impact on sedimentation into a lake (above), however the effect is local and would not create a similar signal in marine sediments. This is also true of unusual meltwater events and post-fire erosion. Therefore we conclude that for units with physical properties that look similar to those in marine sediment cores, with supporting radiocarbon dates:

The similarities in physical properties and supporting age control between the deep-sea sediment cores and lacustrine

cores suggest they are correlative, and therefore synchronous, events. Long-distance correlation between sedimentary

records from such different depositional environments supports that these events are earthquake-triggered. The inter-

pretation that they are earthquake-generated deposits is supported by research in eastern Canada, Lake Lucerne, Dead

Sea, Lake Biwa and Chile.

Our primary objective is to investigate the spatial extent and character of seismogenic deposits in inland lake sediments to

hopefully determine segment boundaries and the down-dip extent of the locked zone, and therefore magnitude potential, of

the Cascadia Subduction Zone.

Through focused coring and CHIRP seismic profiling of some of the lakes we’ve identified (red dots on map figure) we would like to:

1. To compare the characteristics and timing of features within the sediments within lake cores to the seismoturbidites in marine

sediment cores to test for synchroneity and earthquake origin.

2. To use the spatially densified paleoseismic record to investigate segment boundaries along strike.

3. To collect a sufficient number of lake cores to address the spatial distribution and relative magnitude of shaking from past CSZ

earthquakes as recorded by the lacustrine sedimentary archives.

4. To test the hypothesis that correlated signatures may represent “paleoseismograms”.

Experimental Data (Goldfinger, 2011b)

Time

(s)

600

400

200

800

Amplitude(10-10 m s-1)

(Stein & Okal, 2005)

0 500

-2

-1.5

-1

-0.5

0

0 300100 200 SI X 10-5

0 5 10 15 20 25 SI X 10-5

section break

dept

h (m

)

Time

1st rupture

2nd rupture

3rd rupture

Example from Sumatra 2004 Earthquake (Patton et al., 2012)

#*

#*#*

#*#*

#*

#*#*

#*#*#*

#*#*

#*

#*

#*#*#*#*

#*

#*#*#*#*

#*

#*#*

#*#*#*

#*

#*#*#*#*#*

#*#*#*#*

#*#*

#*#*

#*#*#*

#*

#*

#*#*#*#*

#*#*#*#*#*

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

#*

#*

E

E

E

E

EEE

E

E

E

E

E

E

EE

E

E

E

EEE

E

EE

E

E

E

E

E

E

E

E

E

E

E

EE

!

!

!

!

!

!

!

!!

!

!

!

!

!!

!

!

!

!! !

!

!!

!

!

!

!

!

!

!

!

!

!

!

!!

!!

!

!!

!

!

!

!!

!

!

!!

!

^̀!

!

!

!

!

!

!

!

!

!

!

!!

!

!

Lake Washington

Washington

Oregon

California

Tofino

Uclulet

Coquille

Coos Bay

Nestucca

Eel River

Alsea Bay

Long Beach

Cultus Bay

Kanim Lake

Sixes River

Netarts Bay

Ecola Creek

Willapa Bay

Johns River

Catala Lake

Humboldt Bay

Lagoon Creek

Bradley Lake

Siletz RiverSalmon River

Stanley Lake

Willapa Spit

Grays Harbor

Kakawis Lake Port Alberni

Copalis River

Saanich Inlet

Rockaway Beach

Columbia RiverColumbia River

Grayland Plain

Swantown Marsh

Effingham Inlet

Discovery Bay

122°0'0"W124°0'0"W126°0'0"W

48°0'0"N

46°0'0"N

44°0'0"N

42°0'0"N

Upper SquawLake

SangerLake

((((

((((

((((

((

((((

((((

((((

((((

((((

((((

((((

((((

((((

((((

((((

((((

((((

((((

Legend

E Coastal Paleoseismic Sites

#* RR0207 Cores

#* M9907 Cores

#* TN0909 Cores

! Other Prospective Lake Sites

^̀ Focus Lake Site With Existing Data

RR0207-56PC

M9907-31PC/TCTN0909-01PC/TC

Ü

0 50 100 150 20025Kilometers

Klamath

Rogue

Smith

Hydrate Ridge

TN0909-02PC/TC^̀

M9907-33PC/TC

Trinidad

!^̀

BolanLake

!

^̀TriangleLake

Deep-Sea Marine Sites

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 back-ground hemipelagic sediment. Physical properties (grain-size proxies) through these deposits show distinctive excursions which, along with sup-porting radiocarbon dates, are correlated along strike with long-distance correlation supporting earthquake-triggering. 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.

Coastal Lakes, Marshes and Estuaries

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 earth-quakes. These records represent hundreds to thousands of years, but rarely span more than 5,000 years. Correlation of coastal events is mainly depen-dent 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.

Inland Lakes

A Cascadia earthquake of Mw=9 would cause severe shaking along the coast and evidence from the 2011 Tohoku earthquake suggests a similar earth-quake on the Cascadia Subduction Zone could produce strong shaking of 1.0–1.5 g as far as 20-40 km from the coast, strong enough to potentially cause liquefaction and landslides throughout the Coast Range. Studies of seismic shaking in Cascadia inland lakes, however, are limited to just Lake Washington (e.g. Karlin et al., 2004). Many lake records span the Holocene, contain the Mazama Ash datum, and event identification and characteriza-tion benefits from the contrast between the more organic-rich background sedimentation and terriginous material. Radiocarbon dates using plant ma-terial typically provides age control.

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 nu-merous sediment slumps and debris flows, and high-resolution seismic profiles show large retrogressive slope failures. Sediment cores from throughout the lake show sedi-mentary deposits with magnetic susceptibility signatures that can be correlated through-out the lake which have been interpreted as a result of shaking-induced sediment fail-ures. Large local events on the Seattle Fault, as well as subduction zone events, appear to be recorded in this lake.

Effingham and Saanich Inlets: Fjords on Vancouver Island, British Columbia, Canada. Submarine debris flow deposits have been interpreted to be earthquake-generated, 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.

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

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 strati-graphic features of interest.

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

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 (see map inset in panel to the right).

Bolan Lake, OR: Bolan Lake is located approximately 20 km NE of Sanger Lake. It is an entirely spring-fed cirque lake (1638 m elevation) with a small drainage.

Multiple experimental runs, 30 gallon prototype tank. Image shows the resulting deposit from four simulated turbidites. A: Two pulse impulsive event with 30 seconds elapsed between input pulses. B. Single pulse impulsive event. C: Simulated hyperpycnal event, with gradually increasing hydrograph, then gradual decrease. D. Two pulse impulsive event, too compacted by overlying runs for further analysis. Plots at right are four pixel profiles through the deposit at its greatest thickness. Pixel value shows grain size distribution, with material of silt size (SilcoSil 250) having values of ~ 180-210, and aluminum oxide very fine sand in the tan color, ranging from ~ 100-150. Plots show sharp bases for the impulsive events, and the waxing then waning nature of the simulated hyperpycnal event. 30 second separation between pulses is clearly visible in the image and observable in the data.

Hydrate RidgeBasin West

TriangleLake, OR

100 cm

200 cm

300 cm

400 cm

0 cm

g/cc

T4

T5

T6

T7

T8

T9

T10

T11

T3

T10b

T10d

T10a

T9a

T5a

T5b

T7a

T6a

T10f

T8a

T12

T8b

T4a

T3a

T5c

T9b?

T10c

?

?

RR0207-56PC-TC

T1T2

T2a

210Pb(excess)0002 001 Grey Level

TRI-1

?

1.01.8

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

100 10

1300(1260-1350)

HRW-10: 5330 (5210-5430)

HRW-13: 5690 (5570-5810)

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

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

HR W-19: 800 (700-1000)

1060 (950-1180)

4160 (4000-4330)

4460 (4290-4620)

4740 (4570-4910)

5920 (5790-6050)

5700 (5560-5830)

2550 (2410-2720)

1210 (1100-1340)

1470 (1330-1620)

1650 (1490-1810)

HRW-24:300 (230-410)

5930(5710-6190)

(2720-2790)

from Chlieh, et al., 2007

Gamma Density (g/cm3)

Explanation

High-resolution point mag. susc. (SI)Low-resolution mag. susc. (SI)

Sample #: 14C age & 2 rangeHRW 11: 7298 (7220-7377)

Hemipelagic age & est. 2 range7298 (7220-7377)

CT Density (Grey level)

delta landslide

underwater failures

A large subduction zone earthquake would likely cause an increase in sediment transported to lakes in addition to desta-bilizing deposits within the lake, however the majority of this sediment would be deposited on the delta as the flow slowed when entering the lake. Our current interpretation is that the stratigraphic features of interest in the lake cores are a result of resuspension of sediments internal to the lake, then transported down-slope and deposited in the deepest part of the lake.

Understanding the mechanisms creating the characteristics observed in correlated marine and

lacustrine sediments has important implications as it affects our interpretation of past earthquakes

from the stratigraphic record.

Preliminary work has been done at Triangle Lake, OR comparing a newly acquired core from this lake to preliminary seismic reflection data (using a newly acquired Knudsen CHIRP system) and our offshore data. We found a good correspondence between the number and sequence of mineralogic events in the lake and turbidites offshore. Just enough age control exists to tentatively anchor the record temporally. In detail, we found that the Triangle record most closely resembles the Hydrate Ridge offshore core at a similar latitude.

Relevant Paleoseismic Archives

EQ!

EQ!

1480 (1310-1620)

Is marine event T5 (~1500 ybp) one

event or three? Detailed analysis of a high resolution inland lake site, such as Upper Squaw Lake, may provide additional information to help us interpret these sequences.

A. B. C.T1T2T3T4T5T6T7T8T9T10T11T12T13T14T15T16T17T17aT18

T5bT9aT8a or b?T10b

T3aT4aT5aT5cT8a or bT10aT10cT10dT10f

T2aT8a or bT15a

NB

HB

CB

NB

HB

CB

NB

HB

CB

NB

HB

CB

500–530years(110–1,150)

410–500years(110–1,150)

220–240 years(40–600)

300–380years(40–1,150)

? ? ? ?<200 years

T6aT6bT7aT9bT12aT14aT16aAdditionalunresolved events

Barkley

JDF

Astoria

HR

Rogue

Barkley

JDF

Astoria

HR

Rogue

Barkley

JDF

Astoria

HR

Rogue

Barkley

JDF

Astoria

HR

Rogue

SmithKlamathTrinidad

Eel

SmithKlamathTrinidad

Eel

SmithKlamathTrinidad

Eel

D.129 128 127 126 125 124 123 122 121 129 128 127 126 125 124 123 122 121 129 128 127 126 125 124 123 122 121 129 128 127 126 125 124 123 122 121

128 127 126 125 124 123 122128 127 126 125 124 123 122128 127 126 125 124 123 122128 127 126 125 124 123 122

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48

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44

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40

48

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46

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44

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40

48

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45

44

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48

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46

45

44

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42

41

40

48

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46

45

44

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40

48

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48

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40

Inferred segment boundaries from Goldfinger et al., 2011a