Using tsunami deposits to determine earthquake and tsunami

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 4 th c. B. C. Japan 7 th century China, Central & South America Philippines, Indonesia Russian Far East & Alaska North America, New Zealand 16 th century 17 th century 18 th century 19 th 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 deposit grassy field c. 300 years ago Copalis River bank, Washington State coast

Coring at Willapa Bay for the longer tsunami record Mary. Ann 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-20 th 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 PAC

LARGE Polar with plate boundaries NAM EUR BER OKH PAC

uplifted marine terraces uplift rates mm/yr (m/kyr) for last 500 k 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