Using tsunami deposits to
determine earthquake and tsunami
recurrence intervals:
opportunities and challenges
Jody Bourgeois
Earth & Space Sciences
University of Washington
Seattle, Washington
Soldatskaia Bay
Kamchatskii Peninsula
We can use (historic and pre-historic)
deposits from tsunamis to:
•Document tsunami hazard where unknown historically
and where prehistoric tsunamis are larger
•Help produce probabilistic hazard maps
•Calculate tsunami recurrence intervals
(typically centuries long)
•Understand tsunami behavior
•Calibrate, test and enhance tsunami runup modeling
•Educate the public
We can use (historic and pre-historic)
deposits from tsunamis to:
•Document tsunami hazard where unknown historically
and where prehistoric tsunamis are larger
•Help produce probabilistic hazard maps
•Calculate tsunami recurrence intervals
(typically centuries long)
•Understand tsunami behavior
•Calibrate, test and enhance tsunami runup modeling
•Educate the public
QUESTIONS:
WHERE? HOW BIG? HOW OFTEN?
intro
QUESTIONS:
WHERE? HOW BIG? HOW OFTEN?
intro
Problem: Historic records are short and
tsunami recurrence intervals are long.
Oldest catalogued tsunami*:
Mediterranean
4th c. B.C.
Japan
7th century
China, Central & South America
Philippines, Indonesia
Russian Far East & Alaska
North America, New Zealand
16th century
17th century
18th century
19th century
*classified as definite
Lander and Gusiakov, 1997
and online catalogues
How can geology
help tell our
(hi)story?
Copalis deposit
mudflat deposits in years after tsunami
tsunami deposit
grassy field c. 300 years ago
Copalis River bank,
Washington State coast
Coring at Willapa Bay for
the longer tsunami record
MaryAnn coring
This and other cores tell us
that large earthquakes and tsunamis
occur on the Washington coast
every 100-1000 years
(average ~500 years)
There are similar records for
all of Cascadia and also the Gulf of
Alaska
~300 years ago
Willapa longer record
Atwater, Carver, Clague, Darienzo, Gilpin,
Hemphill-Haley, Hutchinson, Kelsey,
Nelson, Peterson, Williams, Witter,…
Turbidites: Goldfinger, Karlin
~3500 years ago
(compiled by Brian Atwater)
Hokkaido
n. Japan-Kuril-Kamchatka subduction zone history
Hokkaido
Tsunami
deposits
take the
record back
thousands
of years
n. Japan-Kuril-Kamchatka subduction zone history
pre-20th century
tsunami deposits
found farther
inland
Nanayama, Atwater, Satake
and several others
Kamchatka
n. Japan-Kuril-Kamchatka subduction zone history
profiles
tephra
stratigraphy
excavations
tsunami
deposits
FIELD METHODS
marine terraces
Polar w/o ice K-centric
Polar w/o ice K-centric
Polar w/o ice K-centric
“hungry America” model
(USGS website)
Hungry America
after Fujita
Mackey
& others
Polar with plate
boundaries
EUR
NAM
OKH
BER
PAC
Polar with plate boundaries
OKH
Polar with plate boundaries
BER
How many and what kinds of plate boundaries?
How does Kamchatka
coastal neotectonics
Three
backpackers
elucidate this problem?
Cloudy Kamchatka
LARGE Polar with plate
boundaries
NAM
EUR
NAM
NAM
PAC
LARGE Polar with plate
boundaries
NAM
EUR
BER
OKH
PAC
uplifted
marine terraces
uplift rates
mm/yr
(m/kyr)
for last
500k years
Mw 7.7 tsunamigenic earthquake
KAMCHATKA LAND
1969
Ozernoi
tsunami
model
(Titov)
(snapshots)
one possible source
configuration
Mw 7.7 tsunamigenic earthquake
KAMCHATKA LAND
peat & tephra
Stolbovaya field site
Bering Sea coast
bumpy tundra
Stolbovaya site
Profile 1, trench 104
1969 Ozernoi tsunami deposit ->
1964 Shiveluch volcanic ash ->
paleo-tsunami deposit ->
Shiveluch c. 1650 A.D. ->
paleo-tsunami deposit ->
Ksudach caldera c. 250 A.D. ->
one of 14 profiles at Stolbovaya
total of >50 excavations
Tsunami frequency
per 1000 years
Tsunami frequency
per 1000 years
Stolbovaya recurrence rate ~1/2 KSZ &
greater than many other subduction zones
Mw 7.7 Ozernoi modeled by 1969 Ozernoi tsunami data and
deposits indicates c. 3 m horizontal shortening
Recurrence intervals for such tsunamis (from deposits)
indicates shortening of c. 15 mm/yr over last 4000 yr
“hungry America” model
Hungry America
Fujita, Mackey and others
LARGE Polar with plate
boundaries
NAM
EUR
BER
OKH
PAC
Challenges
Geochronology
Correlation
Statistics
Challenges
Geochronology
Correlation
Statistics
How many observations
are sufficient?
What is the preservation factor?
(Signor-Lipps)
Challenges
Going beyond
tsunami recurrence
to earthquake recurrence
Challenges
Going beyond
tsunami recurrence
to earthquake recurrence
and onward to paleotsunami and
earthquake magnitudes
Challenges
Paleogeography
Paleobathymetry
Paleotopography
and onward to paleotsunami and
earthquake magnitudes
Applications
Paleoseismology
Neotectonics
Archaeology
Coastal geomorphology
Seismic & tsunami hazards
Education & outreach