PRELIMINARY COMPARISON OF DECEMBER 26, 2004 TSUNAMI RECORDSFROM SE INDIA AND SW THAILAND TO PALEOTSUNAMI RECORDS OFOVERTOPPING HEIGHT AND INUNDATION DISTANCE FROM THE CENTRALCASCADIA MARGIN, USA
Curt D. Peterson 1 , R.K. Chadha 2 , K.M. Cruikshank1, Mathew Francis 3 ,G. Latha 4 , Toshitaka Katada 5 , J.P. Singh 6 , and Harry Yeh 7

ABSTRACT
Measurements of recent tsunami runup and inundation from India and Thailand
are compared to corresponding proxy records of paleotsunami sand deposition in
the central Cascadia margin, Oregon. Runup and inundation measurements of the
December 26, 2004 tsunami are reported from 10 localities each in SE India andSW Thailand. Representative flooding elevations and inundation distances are as
follows for SE India; Chenai (2-3m MSL; 150 m distance), Devanaampatnam, (24 m MSL; 150-340 m distance) and Nagapattinam (4-5 m MSL; 800 m distance),
and for SW Thailand; Kao Khaw Beach (7.2 m MSL; >500 m distance), Khaw
Lak Princess (8.2 m MSL; >2000 m distance), and Nangtong (10 m MSL; >2000
m distance). Tsunami sand transport occurred in mean flow depths of 0.4-1.3 m
where flooding overtopped foredunes and beach plains in the SE Indian sites. By
comparison, ovetopping flows in proximal settings (100-200 m from the beach) in
SW Thailand ranged from 2 to 5 m in depth. The maximum transport distances oftsunami sand, i.e., sand sheet extent, were quite variable within and between
tsunami inundation localities in the SE Indian Ocean. Contiguous sand sheets
were not present at some of the SW Thailand tsunami localities. SE India and SW
Thailand experienced minor shacking but no significant damage prior to tsunami
inundation.
Prehistoric tsunami runup in the central Cascadia margin has been estimatedfrom tsunami sand deposits that were produced by four paleotsunami between 0.3
and 1.3 ka. The sand deposits are thought to represent minimum overtopping andinundation distances. The overtopping records come from wetlands developed on
previously uplifted coastal terraces (6-8 m MSL), and in coastal plains fronted byabandoned, i.e., stabilized, dune ridges (4-8 m MSL). For this study we focus onfive Cascadia localities including Cannon Beach, Rockaway, Neskowin, Salishan,
and Ona in the northern Oregon coast. The ovetopping evidence yields onshore
tsunami heights of at least 6-8 m MSL. Sand sheet deposition from the 1.3 ka
paleotsunami at the Neskowin and Ona wetlands exceeds 1.3 km in shore-normal
1

Portland State University, Portland, OR, USA. petersonc@pdx.edu
National Geophysical Research Institute, Hyderabad, India. chadha@ngri.res.in
3
URS Corporation, Honolulu, USA.Mathew_Francis@URSCorp.com
4
National Institute of Ocean Technology, Chennai, India. latha@niot.res.in
5
Gunma University, Kiryu, Japan. t-katada@ce.gunma-u.ac.jp
6J.P. Singh & Assoc., Richmond, California, USA. jpsassoc@aol.com
7
Oregon State University, Corvallis, OR 97331, USA. harry@engr.orst.edu
2distance. Sand sheets from the three remaining tsunami reach 500-900 m inoverland distance from the beach. The tsunami sand sheets are thought to likely
underestimate maximum inundation of the central Cascadia tsunami, but doprovide minimum estimates of flooding distance.
Preliminary comparisons of the Cascadia paleotsunami deposits and the SE
Asian tsunami records tentatively suggest a similar scaling between the near-fieldtsunami in the central Cascadia margin and the 2004 Sumatra-Andaman tsunami
runup in SW Thailand. Flow velocities and inundation from a future central
Cascadia tsunami might be roughly comparable to the SW Thailand experience,
however pre-tsunami damage from nearfield earthquake shaking and/or soilliquefaction in the Cascadia margin could greatly increase structural damage andmortality from subsequent tsunami inundation.
Introduction
The tragic Mw 9 earthquake and resulting tsunami from the December 26, 2004 SumatraAndaman rupture (Stein and Okal, 2005) provides potential modern analogs to prehistoricruptures of the Cascadia margin (Figure 2). In this paper we examine proxies for tsunami runup
at observed localities in SE India and SW Thailand (Peterson et al., 2005, Yeh et al., 2005;
Francis et al., 2005), and at paleotsunami deposit sites on the northern Oregon coast (Peterson etal., 1995; Alhadeff et al., 1998; Schlichting and Peterson, 2006). These proxies include geologic
records of distinctive sand sheets deposited by the modern tsunami and paleotsunami. The
modern 2004 tsunami yielded both the geologic records of sediment transport and corresponding
ephemeral data on runup height, i.e., maximum still water (MSW) height, and flooding distance,i.e., maximum inundation distance. The Cascadia paleotsunami are currently lacking constraints
on runup height and maximum inundation distance.
Microfossil, geochemical, and debris-caps have been proposed for use to establish
paleotsunami records of MSW height and/or maximum inundation distance in the Cascadia
marign (Hutchinson, et al., 1997; Abramson, 1998; Schlichting, 2000). Rigorous tests of thesetechniques have not been completed for overland tsunami runup in proximal settings, i.e., backbarrier beach plains and low marine terraces. At the present time only the tsunami sand sheet
deposition by barrier over-topping and high-velocity inundation provide established constraints
on overland paleotsunami flooding in proximal settings.
We compile minimum overtopping heights and minimum inundation distances from thecentral Cascadia margin based on existing reports of tsunami sand sheet deposition. These
minimum-inundation proxies are compared to measured runup heights and maximum inundation
distances of the December 26, 2004 tsunami in SE Indian and SW Thailand. Such calibrations of
paleotsunami runup should permit some rough approximations of tsunami flow damage andmortality that could accompany Cascadia near-field tsunami in the future.

Results
India and Thailand
Ten localities in the Tamil-Nadu coastline of SE India (Figure 1 and Table 1) weresurveyed for runup flooding and sediment deposition from the December 26, 2004 tsunami (Yehet al., 2005). Maximum still water (MSW) height ranged from ~3.0 to ~5.0 m above the Indian
datum, i.e., above approximate mean sea level (MSL) (Table 1). Maximum inundation ranged
from 150 to 800 m in shore-normal distance from the beach swash zones. Measured tsunami
flow depth, i.e., the difference between MSW height and the ground surface elevation, range
from 0.4-2.0 m depth in the SE Indian study localities.
Table 1: Inundation Parameters for the December 26, 2004 Tsunami at Selected Sites in SE India
and SW Thailand

Locality

Latitude

Run upHeight(m MSL)1

Inundation
Distance(m)2GroundElevation(m MSL)3

Flow Depth
(m)4

India
PulicatChennai
Kovalam
Kalpakkam
Periakialapet
N.Devanaapatnam
S.Devanaapatnam
Parangipettai
Tarangambadi
Nagapattinam

13.384° N
13.021° N
12.791° N
12.505° N
12.029° N
11.749° N
11.740° N
11.513° N
11.027° N
10.775° N

2.7
2.9
3.4
3.1
3.7
2.3
--4.4
4.3

160
150
180
360
170
160
340
600
400
800

2.3
2.1
2.1
2.4
3.7
1.8
1.5
1.8
3.5
2.3

0.4
0.8
1.3
0.7
-0.5
--0.9
2.0

08.891° N
08.803° N
08.743° N
08.704° N

7.2
7.9
7.5
8.2

>500
>1000
>1000
>2000

~5
~4
~5
~6

~2
~3
2.5
~2

08.663° N
08.637° N
08.627° N

10
10
10

>2000
>2000
>1500

~5
~6
~7

~5
~4
~3

07.949° N
07.946° N
07.884° N

8.0
8.0
5.0

>500
>500
>100

~4
~5
~3

~4
~3
~2

ThailandKo Kao Khaw
Kao Khaw Beach
UnnamedAndaman Princess
Khaw Lak Princess
Khao Lak
Bang Niang
Nangtong
Army Relief Cent.
PhuketBang Tao
KamalaRoyal Thai Rest.
1.

Runup Height, i.e., maximum still water elevations, as given in meters above approximate, mean sea
level (MSL) are taken from mud lines on standing structures.
2.
Inundation distances, as given in meters (m) are taken from maximum landward extent of tsunami
debris, i.e., flotsam, in shore-normal distance from the beach.
3.
Ground Elevation is measured (SE India) or estimated from photographs (SW Thailand) at proximal
distances of 50-100 m from the beach. The ground elevations represent overtopping points atabandoned foredune ridges or beach plains.
4.
Flow Depth is taken from the difference between measured runup height and ground elevation. Thisvalue represents the mean flow depth at the over-topping point, as calculated from maximum stillwater depth and proximal ground elevation. Surge elevations, and corresponding surge depths are
greater than mean still water elevations. Flow depth of surge (not still water depth).

PulicatDevanaapatnam
Nagapattinam
Ko Kao Khaw
Khao Lak
Phuket_9.0 [Figure 1. Location of places discussed in the text, and in tables 1 & 2. The location of the 2004
earthquake epicenter is shown with a star off the coast of NW Sumatra. This point was theinitiation of rupture, which propagated north to the Andaman Islands.
Three of the SE Indian localities, at Chenai, Devanaampatnam, and Nagapattinam, areselected for comparison to the central Cascadia paleotsunami records. These three localities eachcontain 1) relatively-flat, low topographic profiles (1-2 m MSL) behind low foredunes, and 2)
slightly raised profiles (3-5 m MSL) developed on higher stabilized dunes (Peterson et al. 2005).
Tsunami flow depth (0.4-1.3 m), relative flow competence (sand or cobble transport), andassociated structural damage are shown for proximal settings, i.e., ~ 100m distance from thebeach (Table 2). The structural damage ranged from none (none), to damaged details (details), tocollapsed unreinforced masonry (URM) in ascending order of impact. The structural damage
scaled up with increasing tsunami flow depth, increasing maximum inundation distance, andincreasing flow competence in the representative SE Indian localities.
Tsunami runup height, flow depth, and tsunami impact are reported for ten localities in
the Ko Kao Khaw, Khao Lak, and Phuket areas of SW Thailand (Figure 1). Runup height ranged
from 5 to 10 m MSL in the ten localities (Table 1). Inundation distances ranged from >500 to>2,000 m in shore-normal distance from the beach, as based on observed tsunami flotsam/debrislines and/or saltwater wilted vegetation. Water columns of overtopping flows ranged from 2 to 5
m depth in the proximal settings.
Three representative SW Thailand localities are evaluated for tsunami impact. These
localities are developed on relatively-flat beach plains of 4-6 m elevation above sea level.
Vegetation is sparse in the proximal settings, but URM and reinforced concrete structures (RCS)
in residential and commercial developments are common in the selected localities. Relative flowcompetence at the three sites is characterized by boulders, i.e., the largest of the remobilized clast
sizes. The remobilized boulder-size clasts were derived from collapsed URM but were entrainedfor 10’s meters by tsunami flow. The photographed structural damage ranges from displacedconcrete structures (DCS) to damaged RCS in the proximal settings of the three localities. The
scarcity of heavy vegetative debris suggests that the extensive structural damage at these
localities resulted directly from the tsunami flow forces.
Table 2: Representative Tsunami Impact Localities in SE India and SW Thailand
Proximal Settings, 100 m Distance
Inundation
Flow
Maximum Structural
Distance (m)Depth1
Clast Size2 Damage3(m)(Type)(Type)

Locality

Latitude

India
Chennai
N. Devanaapatnam
Nagapattinam

13.021° N
11.749° N
10.775° N

150
160
800

0.8
0.5
2.0

Sand
Sand
CobbleNone
Details
URM

ThailandKao Khaw Beach
Khaw Lak Princess
Nangtong

08.891° N
08.704° N
08.637° N> 500> 2000> 2000~2~2~4

Boulder
Boulder
Boulder

Displaced
RCS
RCS

1.

Flow Depth is taken to be the difference between runup height and ground surface (Table 1). It
represents the depth of the mean or sustained flow. Spatial and/or temporal variation in flow depth,
i.e., surges, are reported from the SE Indian tsunami localities (Peterson et al., 2005).
2.
Maximum Clast Size of transported or remobilized clasts, i.e., sand, cobble, or boulder, are used as
relative indicators of flow competence in proximal settings, i.e., ~100 m distance from the beach.
3.
Structural damage is identified by type, i.e., damage of siding or roofing (Details), collapse of
unreinforced masonry (URM), displaced concrete structures (Displaced), and failure of reinforced
concrete structures (RCS).

For the India and Thailand tsunami analogs we do not use the extent of tsunami sandsheets to characterize the flooding inundation. In SE India the landward extents of the tsunami
sand sheets ranged from 37 to 80 percent of the maximum inundation distances (Peterson et al.,2005). In SW Thailand the tsunami sand sheets were relatively thin and discontinuous in theproximal settings and patchy or non-existent in the distal settings. The thin, discontinuous sandsheets in the proximal settings might reflect supercritical flow velocities, and/or limited
nearshore sand availability in the SW Thailand localities. Sand dilution, by settling andentrapment during transport over long distances (1,000-2,000 m), might account for the lack ofsand sheets in the distal settings. The sand sheets do provide reliable evidence of tsunami flow
overtopping in proximal localities of both SE India and SW Thailand, but they under represent
the maximum inundation distances in distal settings of both study areas.
Cascadia Margin
Five localities have been mapped for paleotsunami sand sheet deposition in Northern
Oregon, in the central Cascadia margin (Figure 2). These localities contain wetlands developedon back-barrier beach plains or flood plains (1.5-3 m above present MSL) at Cannon Beach,
Rockaway, Neskowin, Salishan, and Ona, and/or on low marine terraces (6-7 m MSL) Salishan,and Ona (Table 3). The wetlands are fronted by stabilized dune ridges that contain paleosols at 68 m above present MSL. The paleosols indicate dune abandonment and stabilization prior to thearrival of non-native dune grasses that increased the height of some modern foredunes. We use
the evidence of paleotsunami sand deposits on the landward side of the paired stabilized
foredune ridges or on the low marine terraces to establish tsunami overtopping. The low ridge isused to establish the landward extent of paleotsuami sand deposition, and the high ridge or
marine terrace is used to establish minimum overtopping elevations.
The stabilized foredune surfaces, i.e., paleosol elevations, are used to estimate minimum
heights of overtopping. Dating of the paleodune surfaces by TL or OSL methods is pending
future funding. For this paper we only discuss the last four Cascadia tsunami events, which datefrom 0.3 to 1.3 ka (Schlichting, 2000). Tsunami overtopping heights ranged from 6 to 8 m above
MSL in the study area. Inundation distances ranged from <300 to greater than 1,300 m in shorenormal distance from the present beaches. These paleotsunami sand deposits represent limiting
conditions, i.e., minimum values, of runup height and inundation distance for the four Cascadia
events.

SeasideCannon BeachRockaway

PortlandWashington
Portland

JUAN DE FUC
A
PLATE
PACIFIC
PLATE

OregonNeskowin

California

Salisahn

Ona
0

50

100

Kilometres

Figure 2. Location of places discussed in the text, and in table 3. The sites in table 3 are on the
Northern Oregon coast, which is in the central Cascadia MarginTable 3. Cascadia Paleotsunami Overtopping and Inundation Records from 0.3-1.3 ka

RegionLocality / Site

LatitudeCannon BeachHigh Ridge

45.891° N

Low Ridge

Rockaway
High Ridge

0.3
0.8
1.1
1.3
0.3
0.8
1.1
1.3

Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge

10-15
10-15
10-15
10-15
5
5
5
5

No Record
No Record
No Record
No Record
500
800
900
1,100

0.3
0.8
1.1
1.3
0.3
0.8
1.1
1.3

Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge

7-8
7-8
7-8
7-8
6
6
6
6

No Record
400
600
>700
500
600
700
>700

0.3
0.8
1.1
1.3
0.3
0.8
1.1
1.3

Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge

7
7
7
7
5
5
5
5

No Record
900
900
>1000
800
1000
1,100
>1,300

0.3
0.8
1.1
1.3
0.3
0.8
1.1
1.3

Terrace
Terrace
Terrace
Terrace
Dune Ridge
Dune Ridge
Dune Ridge
Dune Ridge

8
8
8
8
6
6
6
6

No Record
No Record
>300
>300
>300
?
>300
>300

45.106° N

Low Ridge

SalishanTsunami Sand Sheet Deposition
Overtopped Ridge/Terrace
Maximum
Dune Ridge/
Elevation
Transport
Terrace(m MSL)
Distance (m)46.613° N

Low Ridge

Neskowin
High Ridge

Cascadia
Event
Age (ka)

44.891° N

Table 3,ctd.

RegionLocality /
Site
Ona

Latitude
DecimalDegrees44.504° N

Cascadia
Event
Age (ka)
0.3
0.8
1.1
1.3
0.3
0.8
1.1
1.3

Tsunami Sand Sheet Deposition
Overtopped Ridge/Terrace
Maximum
Dune Ridge/
Elevation
Transport
Terrace(m MSL)
Distance (m)Terrace
Terrace
Terrace
Terrace
Ridge
Ridge
Ridge
Ridge

7
7
7
7
4
4
4
4

No Record
?
360
>500
750
>1000
>1000
>1,300Conclusions
Paleotsunami deposits from the last four Cascadia earthquakes (0.3-1.3 ka) serve as
proxies for minimum values of tsunami runup height and inundation distance in the central
Cascadia margin. Inundation distances in particular are likely to be underestimated from theextent of paleotsunami sand sheets in some settings. The minimum estimates of paleotsunami
runup height (6 -8 m MSL) and shore-normal inundation (500-1,300 m distance) are similar to
the recent (December 26, 2004) Sumatra-Andaman tsunami in SW Thailand. Three of the four
central Cascadia paleotsunami were substantially greater in runup height and inundation distancethan the recent tsunami in the SE India localities. The overtopping elevations of at least two of
the Cascadia paleotsunami (> 8 m MSL) would yield flow depths of at least three meters inbeach plain communities of Oregon that average about 5 m MSL. Scaling from the SW Thailand
tsunami experience would suggest substantial structural damage and mortality from a future
Cascadia tsunami in these coastal communities. Additional structural damage and mortality,
relative to the SW Thailand analog, would be expected in the Central Cascadia margin due tonearfield earthquake shacking and/or soil liquefaction prior to tsunami inundation. Pre-tsunami
structural damage could initiate widespread panic, hinder rapid evacuation, and preclude many
vertical evacuation opportunities in the Cascadia margin. Work is now underway in the Central
Cascadia margin to better constrain proximal runup elevations of paleotsunami based on
geologic records in upland wetland settings of elevated marine terraces.
Acknowledgements
Field assistance and language translation was provided by G. Raghuraman. Travel
support was provided by the United States Earthquake Engineering Research Institute, India
National Geophysical Research Institute, India National Institute of Ocean Technology, Oregon
State University, Portland State University, and J.P. and Associates Inc.

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