*Brian Sherrod reviewed the project budget. He noted that this FY we received all the funding requested, and it is likely that we would be funded at the same level next FY (~$90k). All of FY19 funding has been distributed and should be actively being used.
*Joan Gomberg announced a special upcoming NHMA briefing on subduction zone science, on May 7. The purpose of the briefing is to provide background to program Coordinators and other management on progress made and plans going forward, to help set priorities for future planning.
She also advertised next week's SSA meeting in Seattle, which will feature numerous sessions focused on Cascadia.
*Maureen Walton summarized the status of the Powell Center project. The first workshop was held at the end of March, that was focused on the earthquake cycle. 16 participants spent the week discussing recurrence models as defined in the literature and applied globally and to Cascadia, took a hike, and had focused discussions about topics related to defining Cascadia's earthquake cycle. Products included an outline for a review paper, possibly for Nature Geoscience, and an EOS summary.
The ArcGIS database being built was discussed at the workshop, which will contain relevant publicly available onshore and offshore data for Cascadia, either residing in the database or accessible via links. A poster about the database will be presented at the SSA.
The next workshop will be in October or November, 2019, with a focus on rupture and radiation.
*Erin Wirth briefed the group about a proposal just submitted in response to the USGS's call for Risk Research and Applications, that grew out of calls at the Powell Center workshop to improve involvement of social scientists in the project. The project would leverage work from the Cascadia Recurrence Powell Center and internal projects, and the UW's M9 project, to create a story map about the science and impacts of great Cascadia megathrust earthquakes. New funding would support two workshops and a new UW professor who would oversee the map production. Decisions will be made and funds dispensed by mid-May, 2019.
*Nathan Miller described a suite of major Cascade offshore and onshore imaging activities planned, some independent of USGS and others with USGS. In 2020 the Langseth RV will be used in a experiment that will image the entire margin. Many of the lines will sample those done previously and/or supplemented with high-res MCS. Additionally, a proposal to the USGS and NSF has been submitted to supplement the Langseth experiment with OBS and submarine nodal (OBN) deployments. A primary goal of the supplemental experiment is to understand how the margin responds to earthquake shaking. Ann Trehu is led a proposal to complement this offshore work with an onshore deployment. If successful, all these would permit building a tremendous systematic, multi-scale image of both the onshore and offshore!
*Janet Watt reviewed USGS multi-beam, shallow imaging, and coring activities for FY18 and FY19. In FY18 MCS, Chirp and magnetometer data were collected in southern Cascadia, along multiple strike parallel and perpendicular lines. In FY19 gaps in these surveys will be filled, and imaging data using the same types of data to the north will be carried out (in some places coincident with lines planned for the Langseth experiment). Coring also is planned for FY19, to get info on stratigraphic ages, and to support the offshore geodesy effort underway. The FY19 coring will take advantage of a BOEM activity to core and image an area off Trinidad Canyon as part of a BOEM wind energy site investigation. BOEM funds could be used to image elsewhere.
A collaboration with Ben Brooks and university groups to deploy 2 new GPS-A sites in 2020, would expand existing coverage of offshore geodetic monuments, to be used to develop community-based monitoring. A workshop is being planned for FY19, to decide the locations of the monuments.
Systematic multi-beam data also are being collected with NOAA to complete their deep-water (deformation front) imaging.
Jenna and Andrea Ogston will be collecting various types of data to understand sediment sources and suspension, by sampling at Astoria Canyon in a prototype experiment. They also will acquire accompanying high-res imaging data to provide info on sediment availability and remobilization.
Discussions are underway with Charlie Paull from MBARI to do ultra-high resolution imaging along the deformation front. Charlie would have to submit a proposal this summer, so currently he, Jenna and others are exploring what baseline data exist to make the best site selection.
Chris has a project with Maureen Walzac to collect cores at Astoria and Willapa canyons to look at the climate record.
Rob asks if the Little Salmon fault has been imaged offshore, and Janet confirms that they did - "not an impressive structure, ... appears to break up offshore". Data to constrain timing of faulting will be acquired soon.
*SeanPaul La Selle updated the group on the paleotsunami investigation of Floras Lake in southern Oregon. They have a new image of the lake bottom, and in 2017-2018 collected a total of 39 cores that extend back ~7000 years. A new CT-scanner was recently acquired, providing very high resolution core sample images (150 micron resolution, with potential for 40 microns), that will permit previously unanswered questions to be addressed. Going forward, they will be continuing core descriptions, and getting dates of tsunami sands using radiocarbon and OSL. Tina Dura is doing complementary diatom analyses. Results will be compare those from Bradley Lake. In some cases storm deposits cannot be discriminated from tsunamis sources, but not in a large number of instances.
*Harvey Kelsey summarized a new 1-year Little Salmon fault trenching project in northern California. This is supported by the EHP external grants program and trenching will occur in August-September, 2019. The goal is to reassess the chronology of motion on the fault for last 2000 years, focusing on whether slip has been synchronous with megathrust events. Chris Goldfinger noted that he has been revising his Cascadia fault map and may have new info to help with connecting onshore and offshore faults.
*Danny Brothers provided a written update of work on Lake Ozette paleoseismology. Three weeks of fieldwork are planned for July 14 to August 3rd, to characterize the lake basin physiography, stratigraphic framework, and mass transport processes. They will collect high-resolution bathymetric mapping, subbottom chirp and boomer profiling and do vibracoring (in water depths down to 200 feet).
Andy Ritchie's old core records (x-ray logs) were re-examined, revealing evidence for turbidite beds deposited during the last 2,500 yr and varved stratigraphy.
Karl Wegmann and Lonnie Leithold from NC State have demonstrated paleoseismic records from both upper plate faults and the megathrust in Crescent Lake, and plan to collaborate on Ozette and Crescent studies, to leverage resources for expanding the scopes of both. The NC State group will collect 1-1.5 m gravity cores in the deepest portions of the lake to look for records of 1700 event, to correlate them with USGS vibracores. Their grad students will spend time in Santa Cruz.
Results from FY19 will be used to assess additional field efforts for FY20.
*Ralph Haugerud has been working on creating an amphibious geologic map for all of Cascadia (in the US), which will be built from existing maps and relevant information. This FY he is focusing on compiling all the map sources and defining stratigraphy that can be used both onshore and offshore.
*Jon Perkins and Alex Grant summarized landslide activities. They efforts to compile landslide inventories for Cascadia, noting that there is an abundance of landslide complexes apparent in the geomorphology. The goal is to assess what fraction may be seismically activated and why. A USGS/university landslide working group has been formed and is working away at this.
Four applications were received to fill their Mendenhall opportunity to work on coseismic landslides.
A group at the UW has made a comprehensive inventory of landslides in the Tyee formation from high-res Lidar, and developed and applied a calibration curve between age and roughness. The note some possible peaks in the histogram of landslide ages, that vaguely could correlate with the earthquakes inferred in the paleoseismic record.
Since the age-from-roughness estimates are very uncertain they are trying a different approach, which makes use of the previously noted relationship between the dominant frequency of shaking and resonant frequency of a landslide deposit. That is, they are asking how spatially tuned landslide susceptibility is to the dominant frequency of shaking. They are modeling the landslide distribution expected for CSZ ground motions, using M9 simulations and this relationship. They note that data from real earthquakes do exist in a few places.
Chris Goldfinger suggests that this work is not relevant to offshore turbidites generation, because studies show that materials deposited in turbidites come from the upper few cm of sediments, not deep-seated landslides.
*Joan Gomberg mentioned ongoing work to study use of seafloor pressure data for geodesy, currently for a dataset from New Zealand. In May she'll begin a similar project in Japan, using their cabled data.
Six applications were received to fill their Mendenhall opportunity to work on earthquake-related land level changes.
*Chris Goldfinger described analyses of turbidites from Trinidad Canyon in southern Cascadia, that suggests initiation by the Petrolia and multiple NSAF earthquakes. Trinidad Canyon shows that two earlier turbidites in cores exist, above 1700 (T1), were likely M7.1 Petrolia earthquake (1972-2005 14C) and may be the 1906 event (1850-1950 14C). He also noted a deposit just below T1, without hemipelagic sediment between it and the turbidite attributed to 1700, suggesting it was some sort of precursor (possibly on the SAF). They also find the same possible pair of events at Noyo canyon and elsewhere. Noteworthy conclusion is that they may be seeing M7 Cascadia events, and events from California.
*Jay Patton updated us on a geodetic and geologic study of a crustal fault in southern Cascadia. Vertical motions from tide gage and GPS data illuminated offsets where transects crossed faults not previously studied. This motivated collection of Lidar, field visits, plans to collect geophysical data this summer, and a proposal to trench. They found a scarp and terraces, and have estimated slip rates of 0.33 mm/year using incision rate analysis and Lidar transect measurements.
Brian Sherrod noted that the next meeting will be a face-to-face gathering this fall, probably in Seattle, with specific dates and a location TBD. It likely will be part of a larger meeting focused on Cascadia hazard, similar to those that have been held for Northern California previously.
*Jeff McGuire presented some images and inferences from his new tomography model for the Gorda part of the slab. Seismic velocity and resistivity (?) changes clearly delineate the down-going plate and regions inferred to be locked, transitional, and where slow slip events occur.
*Art Frankel described inclusion of basin amplification factors in the 2018 NSHM for the Puget Sound region.