Abstracts of Dr. Jody Bourgeois' talks

7pm Thursday February 28th, 2008; University of Alaska Museum Arnold Espe Auditorium

Ten summers of paleoseismology in the Russian Far East -- earthquakes, volcanoes, tsunamis and adventure on Kamchatka and the Kuril Islands

Pioneering tsunami-deposit studies by I. Melekestseev and T. Pinegina led to an extensive (and ongoing), collaborative field campaign on Kamchatka and the Kuril Islands over the last ten years.  My experiences started with a meeting  in Petropavlovsk in 1996, leading to my first field season in 1998, when I saw my first wild grizzly and backpacked where no American had ever been. Since then, our work has included large teams of Russian and American scientists and students, funded primarily by NSF Earth Sciences and Biocomplexity, the Russian Foundation for Basic Research, and institutes of the Russian Academy of Sciences.   Many of my primary collaborators in Russia are pioneering women.  We have worked with bootlace to helicopter budgets, and shared wild salmon and berries with many bears.  We have worked with volcanologists, seismologists, paleoecologists and archaeologists, among others, from several different countries, and together had many adventures, scientific and otherwise.  Our most recent work is a major international collaboration, the Kuril Biocomplexity Project, where we are attempting to reconstruct 5000 years of paleobiogeography and attendant physical change on the Kuril Islands.

Despite its remote access (and bears), this region is one of the best in the world for the study of tsunami geology. The Kuril-Kamchatka region has rich history of 20th-century earthquakes and tsunamis, so most localities have a historical deposit to compare with paleotsunami deposits. In the time frame of our campaign alone, there have been two large earthquakes and attendant tsunamis generated in the Kuril-Kamchatka subduction zone (Kronotsky 1997; middle Kurils 2006). Moreover, because the volcanic arc associated with the subduction zone is also very active, volcanic ash layers (tephra) serve as important correlation and dating tools for historic and pre-historic deposits. Some accomplishments of our work include: 1) quantification of (paleo)tsunami frequency north of the active volcanic arc, in the SW Bering Sea, supporting presence of a plate boundary in this region; 2) ongoing quantification of (paleo)tsunami frequency at more than 30 localities along 1000 km of coastline; 3) documentation of runup for important historical tsunamis in unpopulated regions (e.g., 1737, 1923, 1952, 1969, 1971, 1997, 2006); and 4) modeling of tsunami source regions to attempt matches with runup patterns.

3:30 pm Friday February 29th; 201 Reichardt Bld., UAF

Does Kamchatka belong to North America? This and other neotectonic questions addressed by tsunami and terrace studies

The north Pacific region remains the last major puzzle of plate boundaries on the planet, and paleoseismology and neotectonics help elucidate this puzzle.  From Alaska to northeastern Russia there remain outstanding problems regarding the nature of the plate boundary between Eurasia and North America. In this region, the northwest corner of the Pacific plate interacts either simply with the North American plate, or more complexly with one or more blocks independent of North America.  From our work north of this corner, evidence of uplift, tilting and convergence contradicts the prevailing, simpler model.  On the Ozernoi Peninsula, ~150 km north of the subducting Pacific plate, marine terraces indicate uplift rates of 0.1 to 0.3 mm/a, with faster rates to the east. Historic and paleoseismic records provide evidence for recurring tsunamigenic, thrust earthquakes offshore of the Ozernoi Peninsula, the most recent a Mw 7.7 earthquake in 1969, and an analogous event onshore in 2006.   A multiplate model where an eastward-moving Okhotsk block, including most of Kamchatka, is converging with a clockwise-rotating Bering block better explains these observations than does the unbroken North American plate model.  Recent GPS measurements are consistent with our analyses. Other neotectonic problems we are addressing with paleotsunami and marine-terrace studies include:  What is the nature of the Aleutian/Komandorsky – Kamchatka collision?  What factors govern the coastal morphotectonics of Kamchatka and the Kuril Islands?  How does historical seismicity vary along the Kuril-Kamchatka trench, and does this variation play out in the paleoseismic record?  We are examining these questions with recent as well as prehistoric records of volcanic, seismic and tsunami events.