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Attendees: Maureen Walton, Lydia Staisch, Alex Grant, Alan Nelson, Art Frankel, Andy Cyr, Art Frankel, Bryan Black, Erin Wirth, Evan Lahr, Andrea Ogston, Fred Pollitz, Janet Watt, Jessie Pearl, Jenna Hill, Nathan Miller, Ralph Haugerud, Brandon Nasr, Kevin Schmidt, Janet Watt, Guy Gelfenbaum,Bruce Jaffe

Topical Reports:

  • Powell Center - Lydia & Maureen

Lydia described the Powell Center and summarized the first Cascadia Recurrence Powell Center Project workshop on recurrence models, noting its products were an EOS article and draft outline for a review paper that is now being worked on.  Maureen described the upcoming October workshop on rupture and radiation and its relationship to recurrence, and the status of the project GIS database. The database should be complete by the end of this fiscal year and online early next year.  It will be similar to the Quarternary Fault and Fold database in format.  Maureen also noted that the project has led to a collaboration with social scientists, which thus far has resulted in a successful NSF-funded EAGER project to the University of Washington (with USGS as collaborators), to explore using story maps to explain coastal science and hazards to the public.

  • Sediment Transport, Andrea and Evan introductions - Andrea & Jenna

Andrea Ogston and Evan Lahr are UW faculty and student working to better understand sediment transport.  Jenna showed slides describing recent work to study sediment processes in Astoria Canyon, involving measurements of sediment thickness, storage and transport and combining them with geophysical characterizations of Astoria Canyon.  They deployed a tripod in spring of 2019 and recovered it in August 2019 (from the UW's R/V Rachel Carson), which measures characteristics that impact bottom flows, sediment supply, processes that can remobilize sediment and generate sediment gravity flows, including non-earthquake processes. Another goal is to assess the role of preconditioning.  They also conducted geophysical surveys and collected box cores on the outer shelf and canyon head in the vicinity of the tripod.  Ideally the tripod would be redeployed by late October to capture winter weather, when sedimentation processes are most active. 

  • Dendochronology, Jessie and Bryan introductions - Jessie & Bryan

Jessie Pearl, a new Mendenhall post-doc to start in Seattle this month, introduced herself and the goal of her work, which is to generate a tree-ring chronology for Cascadia earthquakes and apply it to better constrain past events (e.g., are they sequences or single events).  Bryan Black, a professor at Univ. of Arizona, also introduced himself.  He has been working with others to apply dendochronology methods to date paleo-landslides in Cascadia; thus far none have correlated with the 1700 earthquake (some trees are >1000 years old).  He and others have also been looking at the Seattle fault and have found that all trees likely affected by it died simultaneously. Preliminary estimates suggest that the Seattle fault event was 1055-1056 AD, rather than the radio-carbon date of 930 AD, and they are working now to understand the cause for the difference.  Bryan and others are expanding their work currently to other locations and crustal faults in the Puget Lowlands. Bruce Jaffe asks if they're aware of Brian Atwater's earlier work to use tree roots, where bark is not available (they are) and Alan Nelson noted that they should check his 2014 paper, which has Seattle fault earthquake carbon dates that encompass their new dendochronology dates.

Erin summarize her work with Art Frankel and the UW's M9 project, in which they produced ~50 ground motion simulations.  This work has now been published and they're in the process of generating ShakeMaps from the simulations.  Current work is focusing on understanding how shaking is modified by sedimentary basins, and some of their results were recently published.  They have just purchased six new broadband instruments, which will be deployed for basin studies throughout the region over the coming years.  They also are beginning to work on simulations for crustal fault earthquakes, and have been working with UW student Ian Stone to study the impact of topography on ground motion. Erin noted that they have explored various codes for doing their modeling, and are leaning toward using open source codes. Fred asked what the impetus was for the latter, and Erin responds saying that the author of the code they were using did not want to share it with others and this was becoming problematic.

Erin also mentioned the EAGER proposal (see first topic), noting that it was built on the proposal we had written in response to the USGS Risk Project RFP. 

Joan asks if there are any plans to extend work offshore; Erin says that they have no explicit plans, but a better velocity model likely is needed to tackle this.  Erin also described the Community Velocity Model workshop being planned for Nov. 4th. 

  • Landslides - Alex & Jon

Sean Lahusen will join the landslide group as a Mendenhall post-doc, to look at possible landslide signatures of the 1700 earthquake.  They will also be advertising for another post-doc in the next round. Sean currently is leading another project that uses topographic roughness metrics to assess the landslide dates and distributions, specifically to test whether there is an abundance of landslides around the 1700 earthquake.

Currently a project with Sara McBride is underway to study coseismic landslides and liquefaction, their cascading phenomena (e.g. tsunamis), and impacts on communities.  In the near future they hope to go to Vancouver Island where native America legends suggest there may have been landslides there in 1700, and to track down more information about these stories.  Finally they are studying the connection between ground motion frequency and landslide generation.

The suggestion to collaborate with the lake paleoseismologic studies (see below) was noted as a reasonable idea.

  • Offshore Imaging and Coring - Janet, Jenna & Nathan

Janet describe their overarching goal of better understanding quaternary deformation, primarily offshore and with respect to along-strike heterogeneity. She showed a map of bathymetric and subsurface imagery coverage achieved during 2018 and 2019, when they collected multibeam and magnetic data.  Another cruise is scheduled in the coming months. 

This team has a Cooperative Agreement with the UW in 2019, with which they collected high-res CHIRP from Rachel Carson.  At this time high-resolution imagery covers the entire Cascadia margin! One product derived from these data will be characterization of sediment thickness variations along the shelf, and another is detailed characterization of offshore faulting and deformation. 

One more cruise is scheduled this fiscal, with the BOEM, to survey and collect cores along much of the southern half of Cascadia.  Some of sampling will focus on constraining sediment transport and the turbidite record. 

Plans are being developed with Charlie Paull at MBARI to do ultra-high resolution, ROV imaging along Trinidad Canyon, and possibly Eel and Rogue Canyons. Similar work may also be done at identified sites near the deformation front where there is evidence of possible recent deformation. 

Janet showed the tracks planned for the margin-wide 2020 Langseth experiment, and Nathan noted that he is participating a companion NSF-funded project to augment the imaging done during that experiment.

We discussed integrating all these data into the project GIS database, and all agreed that this should be done.  Although the data are not yet ready for distribution, the eventual distribution should be considered now, and perhaps display of track lines, core locations, etc.

  • Lake Ozette - Janet & Nathan

Janet was not able to get updates from Danny or Brian, but did report that a month of successful field work was completed this summer, yielding swath bathymetry of entire lake, ~50 cores, and lots of Chirp imagery.  They also may have collected some data from Lake Crescent.  Nathan confirmed that the data collected are high quality and comprehensive.

A new major, multi-year effort is underway to incorporate geodetic data and modeling into NSHM and UCERF (led by Ned Field).  This is motivated by questions about whether the data and models being used are sufficiently up to date and adequately capture uncertainties.  Fred showed an updated fault map compiled by the NSHM team and noted that likely many faults are missing from the PNW and suggested we might provide more information to them.  One product of this effort will be better definition of the down-dip end of the locked zone. Fred suggests that including vertical GPS displacement estimates, rather than only horizontal ones (as done to date), should reduce uncertainties in locking models.   

  • Offshore Geodesy, GPS-A and Pressure - Janet & Joan

Janet summarized collaboration between the EHP, CMG, Scripps and UW to deploy GPS-A in Cascadia.  She showed a map of currently deployed sites.  In FY20 two new sites will be deployed following a workshop that will be held to decide where to put them.  Joan notes that GPS-A measurements are likely available from David Chadwell at Scripps.

Joan noted that she is working with a team at the UW to explore the potential of seafloor pressure data for measuring seafloor vertical displacements. A completed study concludes that removal of oceanographic signals remains challenging, but improvements are possible. They currently have projects underway using data from Alaska and Japan (where data exist).

  • Coastal Stratigraphy and Tsunamis - Alan

Alan summarized five projects underway that focus on tsunami deposits and land-level changes.  Field sites include Floras Lake, Salmon River estuary, Suislaw River, Bradley Lake Nehalem River estuary,  Willapa Bay, and other sites in northern CA and western WA. He showed results of J. Padget's (University of Rhode Island) and Isabel Hong's (Rutgers University) PhD works that use microfossil transfer functions to date land level changes. These expand the suite of paleoseismic event ages substantially, although some questions about the analyses still need addressing (particularly those based on diatoms).  Art asks how these new onshore data compare with turbidite record, and Alan responds noting that turbidite record has such large uncertainties that they can be said to be consistent; i.e., improvement is needed in turbidite uncertainties to reject consistency.  Joan notes that a lack of onshore evidence for the offshore T2 event still seems to exist. Alan says the one exception to this is a possible observation at Siuslaw River, but it may not be earthquake related, and Bryan thinks dendochronology may help constrain this and will check it out!

  • Tsunamis in Oregon Coastal Lakes - Bruce & SeanPaul

Tsunami modeling is being tuned to match tsunami deposits along the Salmon River, and animations of the inundation show good agreement.  A goal is to use deposit volumes as well as their spatial distribution. Work is also underway in Flores Lake, where numerous cores have been taken and CT scans are being analyzed.  Ultimately the Flores Lake chronology will be compared with that from and Bradley Lake.  In summer of 2020, they plan to begin work in Garrison Lake.

  • Turbidite Chronology Assessment - Joan

A manuscript describing a re-examination of the core-logs and age dates used to derive the Goldfinger et al. (2012) chronology has been reviewed and is now being revised.

  • Post-docs

Nora Neminski will be a Mendenhall post-doc in the CMGP studying source-to-sink sediment transport in Cascadia. She will work primarily with Jenna.

Lydia and others have submitted Mendenhall and Geoprism proposals for post-docs to do 3-D finite-element modeling of the relationships between subduction and overlying plate deformation.

Erin and others will be advertising for a Mendenhall post-doc to study Cascadia ground motions.

The UW is currently advertising for a post-doc to study subduction zone processes.

  • Upcoming Events

November 4-6 PNW Earthquake Events, Seattle - sign up now!

October 6-9 SZ4D Megathrust Modeling Workshop, Eugene

October 9-11 SAGE/GAGE IRIS/UNAVCO workshop, Portland

October 21-25  Cascadia Recurrence Powell Center Worksho

Next Meeting - likely in conjunction with the November 4-6 events in Seattle, but TBD!

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