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Abstracts and Accompanying Information: 2015 PCMSC Seminars

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Painting Models

Fedor Baart
Deltares

Wednesday, December 9th at 2:00 pm

Abstract:

Image showing a painted model.The emergence of interactive art has blurred the line between electronic, computer graphics and art.

Here we apply this art form to numerical models. Here we show how the transformation of a numerical model into an interactive painting can both provide insights and solve real world problems. The cases that are used as an example include forensic reconstructions, dredging optimization, barrier design. The system can be fed using any source of time varying vector fields, such as hydrodynamic models. The cases used here, the Indian Ocean (HYCOM), the Wadden Sea (Delft3D Curvilinear), San Francisco Bay (3Di subgrid and Delft3D Flexible Mesh), show that the method used is suitable for different time and spatial scales.

High resolution numerical models become interactive paintings by exchanging their velocity fields with a high resolution (>=1M cells) image based flow visualization that runs in a html5 compatible web browser. The image based flow visualization combines three images into a new image: the current image, a drawing, and a uv + mask field. The advection scheme that computes the resultant image is executed in the graphics card using WebGL, allowing for 1M grid cells at 60Hz performance on mediocre graphic cards.

The software is provided as open source software.

By using different sources for a drawing one can gain insight into several aspects of the velocity fields. These aspects include not only the commonly represented magnitude and direction, but also divergence, topology and turbulence.


Linking models to understand changes in the San Francisco Bay-Delta Ecosystem

Rose Martyr
CASCaDE Hydrodynamic Modeler, USGS

Wednesday, December 2nd at 2:00 pm

Abstract

Cool schematic from Rose's talk.Many drivers and stressors, both long-term and abrupt, are known to have complex effects on water quality and ecological well-being in the San Francisco Bay, Sacramento and San Joaquin Rivers, and their connected Delta system (hereafter referred to as the Bay-Delta). CASCaDE II (Computational Assessments of Scenarios of Change for the Delta Ecosystem), funded by the U.S.G.S., the Delta Stewardship Council/ Delta Science Program, and the San Francisco Estuary Institute (SFEI), comprises a model-based approach for determining how multiple drivers of environmental change will impact the Bay-Delta ecosystem (http://cascade.wr.usgs.gov/). The project focuses on the evaluation of changes in physical configurations of water conveyances within the Delta, as well as changes in climate, and the responses of the Bay-Delta hydrodynamics, water quality, and ecosystem processes for key species within the Delta.

CASCaDE II implements a new, state-of-the-art, unstructured grid, coupled hydrodynamic-sediment model - Delft3D-FM, developed by Deltares Inc. - that describes the evolution of flow and sediment characteristics as the critical drivers in the Bay-Delta system, and connects with several other models to provide linkages across climate, hydrodynamics, sediment and ecosystems. These other linked models examine climate, hydrology, phytoplankton, bivalves, contaminants, marsh accretion, and fish.

This seminar focuses on CASCaDE's:

  1. application of Delft3D-FM, using historical Bay-Delta hydrological conditions, to generate regional hydrodynamics and water quality characteristics under current and future sea levels; and
  2. proof-of-concept integration of hydrodynamics, sediment, water quality, and habitat suitability models to understand the cascading effects of regional hydrodynamics and water quality changes on Bay-Delta ecosystems.

Photograph of Sean.Coastal Hazard Prediction

Sean Vitousek
USGS Pacific Coastal and Marine Science Center

Wednesday, November 18th, 2015, 2:00 pm

Abstract
Reliable, quantitative predictions of coastal hazards and shoreline change on decadal to centennial time scales are increasingly sought for adaptation planning. Assessments of coastal hazards typically rely on detailed numerical modeling efforts (e.g. the USGS Coastal Storm Modeling System - CoSMoS). In this talk, I discuss the development and application of CoSMoS - COAST, a novel, data-assimilated shoreline model forced by waves, sea-level rise, and sediment supply. The model synthesizes and improves upon several shoreline models in the literature. It is applied to predict shoreline change by 2100 on 400 km of Southern California coastline. In this talk, I also discuss a theoretical investigation of extreme value theory and demonstrate how sea-level rise leads to considerable increases in the frequency of coastal hazards.


Screen shot from Rueda's talk.Methodologies of Coastal Flood Risk Assessment

Ana Rueda
University of Cantabria

Tuesday, November 2, 2015, 12:00 pm

Abstract:
Coastal floods and extreme events are normally due to the combination of different variables {e.g. wave height and period, storm surge, mean sea level}. Therefore, understanding the risk of coastal flooding requires knowledge of the joint occurrence of these inputs. The selection of models and methodologies used to downscale the hazard also play a major role in risk assessment, and in order to estimate the final flood risk, the exposure and vulnerability components deserve equal treatment. In this work, examples of coastal flood risk assessment at two different spatial scales are evaluated.


Slide from Karen's talkA latitudinal approach to assess sea-level rise vulnerability for Pacific coast tidal wetlands

Karen Thorne
USGS Western Ecological Research Center, Vallejo, CA

Wednesday, October 28th, 2015, 2:00 pm

Abstract:
Climate change effects on coastal ecosystems will include rising sea levels and changes in the frequency and severity of storms.  Sea levels are projected to increase up to 167 cm by 2110 along the Pacific coast and storms may increase in frequency and magnitude, threatening or improving the persistence of tidal marshes.  In 2012 we initiated a project that developed a standardized methodology to collect detailed ground data at 18 study sites in Washington, Oregon, and California along a latitudinal and tidal gradient. At study sites we collected local physical and biological data, including elevation, tidal inundation, salinity, vegetation composition and structure, and accretion rates to assess how sea-level rise may alter these estuaries in the future. This data was used to calibrate the Wetland Accretion Response Model for Ecosystem Resilience (WARMER) model that projects wetland elevations under sea-level rise scenarios.  This standardized approach allowed site results to be comparable across the coast but site specific enough to assist resource managers with climate change planning.  Multiple factors, including initial elevation, marsh productivity, sediment availability, and rates of sea-level rise affected marsh persistence to 2110 at all sites. Model results showed that sea-level rise vulnerability varied across the Pacific coast estuaries and was driven by local accretion rates, climate and the extent of anthropogenic modification of the estuary. Our models suggests that most tidal wetland study sites have resiliency to sea-level rise over the next 50-70 years, but that sea level will eventually outpace marsh accretion by 2110. Results from stakeholder workshops will also be presented.


Aerial photos of floodplain of Blackwood Creek.Human-Watershed Interactions: The Role of Ecology, Geomorphology and People

Samantha Greene
Waterways Consulting, Inc.

Wednesday, October 21st, 2015, 2:00 pm

Abstract:
Human-watershed interactions can be divided into four stages: pre-human contact, infrastructure/resource harnessing, unexpected long-term effects, and restoration/remediation.  A thorough understanding of the pre-human landscape allows for the quantification of human impacts and provides a starting template for developing restoration/remediation efforts.  Dam infrastructure is one of the most common types of infrastructure that have altered watershed ecology, hydrology, and geomorphology.  However, riparian land cover conversion to agriculture and timber land can also result in significant and unexpected long-term effects on river ecology, hydrology, and geomorphology.  Some unexpected effects from damming streams or converting riparian land cover include species invasions, disrupted sediment transport regimes, and loss of aquatic and riparian habitat.  Geomorphic surfaces and processes from the pre-infrastructure era can be used to explain unexpected effects and determine the potential for restoration.  Clearly stated restoration goals that consider the modern hydrologic, geomorphic, and human landscape will improve the potential for a successful restoration.


Flier for talkStakeholder-Driven Science Needs to Address Changing Climate in the Pacific Islands Region

David A. Helweg, Ph.D.
Director, USGS Pacific Islands Climate Science Center

Wednesday, October 14, 2015, 10:30 am

BIO:
Dave Helweg is the director of the U.S. Department of the Interior's Pacific Islands Climate Science Center, headquartered in Hawaiʻi. The Pacific Islands CSC provides climate science services to Hawaiʻi and the US-Affiliated Pacific Islands. He is an expert in behavioral biology, bioacoustics and signal processing, receiving his Ph.D. from the University of Hawaiʻi at Mānoa in 1993.

 


Wave-supported gravity currents in continental shelves

Abbas Hooshmand
USGS/Western Washington University

Thursday, October 1, 2015, 12:00 pm

Brief description:
Wave-supported gravity currents (WSGC) are one the most important processes in cross-shelf sediment transport.
An analytical model for predicting sediment transport due to these events on the shelf is proposed and validated
using experimental observations.


Slide 1 from Eric's talk, informing coordinated investments for hazards mitigation, ecosystem restoration, climate adaptation, and indigenous community health.Linking Climate Change, Watershed and Coastal Impact Models for Resilience Planning

Eric Grossman
USGS

Wednesday, Sept 30, 2015, 2:00 pm


Figure from the upcoming talk on subduction zone science.

Advancing USGS Subduction Zone Science

Tom Brocher & Eileen Evans
USGS Earthquake Hazards, Menlo Park, CA

Wednesday, September 9, 2015, 2:00pm

Abstract:
Subduction zones, with their extraordinary dimensions, high rates of activity, and proximity to a significant portion of the global population, host the world’s most potentially hazardous earthquakes, volcanoes, landslides, and tsunamis.  In addition to posing significant geologic hazards, geologic processes along subduction zones shape the world’s surface morphology, control resource development and distribution, and interact with the Earth's climate.  During the past decade catastrophic events along subduction zones have been the catalyst for major investments and consequent scientificdiscoveries, activities that have helped improve hazard assessments. As an ad hoc group of USGS scientists conducting research on subduction zones, our long-term goals are to facilitate the ability of the USGS to capitalize on and lead advances in subduction zone science, while maintaining USGS’s unique existing capabilities, and ensuring that USGS mission goals and constituents’ needs are met.  We believe an important first step toward these goals involves enhancing communication and coordination for USGS work related to geologic hazards along subduction zones.  The unique and diverse environments in subduction zones (e.g., accretionary prisms, plate interfaces, down-going oceanic slabs, overriding plates, volcanic arcs, and flexural outer-rises) provide natural laboratories to observe and learn about a wide range of geological processes and for collaboration among manydisciplines.  Thus, today’s goal is to start this internal dialogue by sharing examples of our own ideas of important scientific issues, and learning about your views on the needs of your constituents, big scientific questions, priority frontiers, and ideas about how to progress towards these goals most effectively.


Aerial photograph of the Elwha River.Measuring Change on the Elwha River during the Biggest Dam Removal Ever:
Structure-from-Motion Analyses in 4-dimension

Andy Ritchie, Olympic National Park

Thursday, August 20, 2015 2:00pm


Map of the globe showing location of Qingdao in relation to Santa Cruz.A general introduction to marine science research in Qingdao, China

Xiangwen Ren
The First Institute of Oceanography, State Oceanic Administration of China

Wednesday, June 17, 2015 2:00pm

Abstract:
In this lecture I will give a general introduction to the marine science research being conducted in Qingdao, China. I will begin by introducing Qingdao followed by a brief introduction to the many oceanographic institutes that are housed there. I will provide detailed information about the oceanographic institute I am visiting from, The First Institute of Oceanography, State Oceanic Administration of China; including information about their deep sea mineral exploration, their research vessels and the instruments they have accessible on board, analysis instruments used in their labs, as well as research conducted by the research group I am a part of. I will conclude by providing a general understanding of my research, dealing primarily with Co-rich ferromanganese crusts, and my purpose for visiting the USGS in Santa Cruz while working with Dr. James Hein.


Slide from Takesue's talk showing a flow chart on how to improve recruitment and retention of women in science.Themes and outcomes from the 2nd USGS Women in Science Dialogue (WISDom)

by Renee Takesue, USGS PCSMC Research Geologist

Thursday, May 28th at 1:00 pm

 


An Overview of Terrestrial Lidar Surveys for Coastal Science Applications

Slide from Palaseanu-Lovejoy's talk showing Bonny Doon Beach T-lidar and airborne lidar.by Cindy Thatcher, USGS Eastern Geographic Science Center

Thursday, May 21st at 1:00 pm

 

Abstract:
A key advantage to terrestrial lidar systems is the very high point density and high accuracy in both the vertical and the horizontal planes, which provides the capability of measuring fine-scale features that may be more difficult to detect with an airborne lidar system. An overview of terrestrial lidar surveys of earthen levees in Louisiana, sea cliffs in California, and coastal forests in the Hurricane Sandy impact region will be presented. The surveys were conducted with a mobile system (a lidar scanner mounted on a vehicle with an integrated inertial measurement unit) or a static tripod-based scanner. For all surveys, independent ground control data were used to quantify the accuracy of the georeferenced terrestrial lidar point clouds. Accurate georeferencing is critical for change detection analyses using repeat surveys, or for the integration of terrestrial lidar with airborne lidar, imagery, and other geospatial datasets. Examples of some of the challenges related to the collection and analysis of terrestrial lidar will be provided. The advantages and disadvantages of terrestrial lidar compared to airborne lidar for surveying coastal topographic features will also be discussed.

 


Research update on the Mid Atlantic Ecosystems Project (movie included!)

Photograph of deep-water fauna, from Prouty's talk.by Nancy Prouty, USGS Pacific Coastal and Marine Science Center

Wednesday, May 20th at 1:00 pm

Abstract:
Submarine canyons are dominant features along the US Atlantic margin, serving as important conduits of pollutants, organic carbon, and sediments from shallow to deeper waters as well as providing habitats for deep-sea corals. In 2010 the Bureau of Ocean Energy Management (BOEM) initiated a 4-year multi-disciplinary “Atlantic Deepwater Canyons” study, which focuses on ecologically significant habitats (cold seeps, hard-bottoms and shipwrecks) in Norfolk and Baltimore canyons. As part of this multi-disciplinary we have studied the movement of dissolved and particulate matter within submarine canyons, composition of organic matter in the canyon and adjacent slope, and distribution of deep-sea corals to understand the off-shelf export of sediments and carbon into these deep-water ecosystems. In addition, we also investigated evidence of seabed methane venting along the US Mid-Atlantic Margin as confirmed by the presence of authigenic carbonates and methantrophic deep-sea mussels, Bathymodiolus childressi, collected near active vent sites. The biological indicators of methane venting presented here expand the understanding of widespread seepage identified by previous geophysical data.


California Cliff Metrics: Mapping and Validation

Slide from Palaseanu-Lovejoy's talk showing Bonny Doon Beach T-lidar and airborne lidar.by Monica Palaseanu-Lovejoy, USGS Eastern Geographic Science Center

Tuesday, May 19th at 11:00 am

Abstract:
Seacliff erosion is a serious hazard with implications for coastal management, and is often estimated using successive hand digitized cliff tops or bases (toe) to assess cliff retreat. Even if efforts were made to standardize manual digitizing and eliminate subjectivity, the delineation of cliffs is time consuming, and depends on the analyst’s interpretation. We propose an automatic procedure to extract cliff edges from high resolution lidar-derived bare-earth digital elevation models, generalized coastal shoreline vectors and approximate measurements of distance between the shoreline and the cliff top. The method generates pseudo-orthogonal transects and profiles with a minimum spacing equal to the digital elevation model resolution and extracts for each profile the xyz coordinates for the cliff top and toe, as well as second major inflections along the profile. This automatic method is repeatable, takes advantage of detailed topographic information within high-resolution digital elevation models, and is more efficient than hand-digitizing.


Neogene fault evolution, offshore south-central California using geology and seismic stratigraphy

Samples of diagrams from Chris' talk.Chris Sorlien
Earth Research Institute, UC Santa Barbara

Friday, April 17, 2015, 11:00 am

with contributions from Richard Behl, Craig Nicholson, Nelson Doris, Courtney Marshall, James Kennett, and Marc Kamerling

Abstract:
Faults offshore south-Central California and in northern Santa Barbara Channel present earthquake hazards to coastal cities and facilities. This includes the offshore 120 km of the (oblique) blind thrust North-Channel-Pitas Point system, thought by some to be capable of M8.0 earthquakes. These faults and associated folds have accommodated oblique NNE-SSW contraction for the last ~5 million years. Faults in Santa Barbara Channel strike E-W, and deformation is a combinations of thrusting and left-lateral displacement. Faults in offshore south-central California strike NNW-SSE and deformation is a combination of thrusting and right-lateral displacement. These two fault domains intersect and interact in the area offshore Pt. Arguello. These faults were mostly present earlier, and experienced oblique extension between ~19 and ~5 million years ago. Thus, the currently active faults are reactivated. The pre-existing structure results in strike-slip motion occurring on faults with surprising geometry. Moderately-dipping strike-slip fault segments are relatively common in offshore southern and central California. For example, the right-lateral Hosgri fault dips east less than 30 degrees at depths below 1 km, to at least 2 km, as imaged on profiles from 3D seismic reflection data. The northernmost of these profiles is 15 km south of the Diablo Canyon nuclear generating station. The deep fault there is kilometers east of the projection of the vertical shallow fault.

Our regional seismic stratigraphic correlations are constrained by the geology sampled in petroleum test wells and our own piston cores. These piston cores sampled seafloor outcrops in central Santa Barbara Channel. Our group used biostratigraphy, oxygen isotopic stratigraphy, and tephrochronology of the 639 ka Lava Creek ash to produce a precise seismic stratigraphic age model back to 740,000 years. Older control from paleontology on sea floor and well samples includes a ~1 Ma horizon from Santa Barbara Channel, a ~1.2 million year-old horizon from Ocean Drilling Program site 1017, and the 1.8-1.9 million year-old top Lower Pico.


Morphologic Response and Recovery Related to Hurricane Sandy at Fire Island, NY

Photo from Fire Island, NY.Cheryl Hapke
USGS, St. Petersburg Coastal and Marine Science Center

Weds., April 1, 2015, 1:00 pm

Abstract:
A variety of morphologic data of the Fire Island, NY barrier island system were collected prior to, and in the time period since, the landfall of Hurricane Sandy - the largest hurricane recorded in the Atlantic basin. Data include topography of the beach and dunes, bathymetry of the nearshore and sub-bottom data to map sediment thickness in the nearshore. These data are used to assess morphologic change related to storm processes from Hurricane Sandy and the winter storms that followed. In addition, we are monitoring the system to develop data-driven approaches for quantifying response, recovery, and resilience which will be incorporated into models for predicting recovery from future storms.
During Hurricane Sandy, the beaches and dunes on Fire Island were severely eroded, and the island breached in several locations on the eastern segment of the island. The surfzone morphology was extensively impacted by Hurricane Sandy and continued to evolve during subsequent winter storms. As is typical during large storm events, the outer bar moved offshore during Sandy. Almost two years after the storm, however, the bar remains further offshore than prior to Sandy, resulting in a widened surfzone. The average volume of the shoreface seaward of the bar increased, which is attributed to the seaward translation of the outer bar and additional offshore transport and deposition of material from the inner surfzone during the storm.
The subaerial beach has experienced substantial recovery since the winter of 2012-13. A new morphometric for tracking the recovery of the upper beach at Fire Island indicates there is a temporal trend towards a wide, flat beach berm which was sustained even through a winter storm season. This trend may represent a new “recovery state” of the beach which is wider than the pre-Sandy beach, providing an increase in the fetch that favors the aeolian processes of dune reformation.

 


Screen shot from upcoming seminar presentation.California Earthquake Probabilities

Tom Parsons
USGS PCMSC

Weds., March 18, 2015, 2:00 pm


Multi-model climate projections of surface ocean waves in Europe

Maps showing model climate projections of surface ocean waves.Jorge Perez Garcia
IH Cantabria

Tues., March 10, 2015, 11:00 am

Abstract: In recent years, the impact of climate change on sea surface waves has received increasingly more attention by the climate community. Indeed, ocean waves reaching the coast play an important role in several processes concerning coastal communities, such as inundation and erosion. However, regional downscaling at the high spatial resolution necessary for coastal studies has received less attention. Here, we present a novel framework for regional wave climate projections and its application in the European region.

The multi-model projection methodology is based on the statistical relation between predictor (atmospheric conditions from reanalysis) and predictand (multivariate wave climate from hindcast). This predictor-predictand relationship is applied to the daily SLP fields from Global Climate Models (GCMs) in order to project future changes in regional wave conditions. The GCMs used in the multi-model projection are selected according to skill criteria. The application of this framework is shown through CMIP5-based wave climate projections in Europe. The low computational requirements of the statistical approach allow a large number of GCMs and climate change scenarios to be studied.

According with previous works on global wave climate projections, the estimated changes from the regional wave climate projections show a general decrease on wave heights and periods in the Atlantic Europe for the late XXI century. The regional projections, however, allow a more detailed spatial characterization of the projected changes under different climate scenarios.


Photograph from the Elwha.Coastal and nearshore response to dam removal on the Elwha River

Melissa Foley
USGS PCMSC Research Ecologist

Weds., March 4, 2015, 2:00 pm

Abstract: The removal of the Elwha and Glines Canyon dams on the Elwha River in Washington caused a massive amount of sediment to be mobilized and transported downstream. The physical effects of increased sediment—including deposition and high suspended sediment concentrations—have altered the physical and biological conditions in the two coastal estuaries and nearshore hard-bottom habitat. Linking changes in physical conditions to biological changes in these habitats is a critical component of monitoring the response and recovery of the system as time progresses.


VAVUQ: Software for Automation of Verification, Validation, and Uncertainty Quantification in Environmental Modeling

Kaveh Zamani
UC Davis

Weds., February 25th at 2:00PM

Abstract: New automation software which is intended for Verification and Validation (V&V), Uncertainty Quantification (UQ) in environmental fluid mechanic models has been developed. VAVUQ, a Python/Matlab code post-processes modeling results and produces a log. It is able to perform code verification via various common techniques, including, Method of Manufactured Solution, Method of Exact Solution, and Cross-Code Verification. In addition, the library is capable of conducting Richardson Extrapolation for Solution Verification. For model skill validation, common statistics are included in the software. As a final point, the new code is able to conduct Complete Richardson Extrapolation (RE) on complex geometries via high-order non-oscillating numerical interpolation schemes. Furthermore, based on the results of RE, the software is calculating lower and upper bounds of numerical error to quantify uncertainty in the modeling results. Some additional capabilities such as calculating GCI, handling adaptive meshes and mixed order schemes are also exist in the software. Couples of examples are provided with the new software plus introductory information on the concepts of Verification and Validation in Environmental Fluid Mechanics.


Rethinking Tsunami Generation by Earthquakes

Eric Geist
USGS PCMSC Research Geophysicist

Figure from Eric's talk.Weds., February 4, 2015, 2:00 pm

Abstract: Dislocations have been used to represent tsunami generation by earthquakes for over forty years. Conventional use of dislocations as a tsunami source, both for uniform and heterogeneous kinematic rupture, requires a priori information about seismic moment, slip, and rupture path. Despite their simplicity and widespread use, such models are not guaranteed to be consistent with any physically plausible faulting scenario, and may span a range of parameter space far beyond what is physically realistic.  In collaboration with researchers at UC Riverside over the last 10 years, a new type of tsunami generation model has been developed from spontaneous, dynamic rupture simulations.  Such models start with the fault geometry, the material properties, the loading stress on the system, and the frictional behavior on the fault.  Based on these input parameters and physical laws, the earthquake rupture and ground motion processes (including the final size of the earthquake, rupture path, spatiotemporal slip distribution, and near-source ground motion time history) are calculated results of the models.  This new representation of tsunami generation opens up a whole new domain of problems that can be addressed, such as determining when subsidiary faults are activated and when megathrusts rupture near oceanic trenches.


Figure collage from Steve's talk.Water resource studies in the Pacific Islands

Stephen Gingerich
Research Hydrologist, USGS Pacific Islands Water Science Center

Thurs., January 29, 2015, 2:00 pm

Dr. Gingerich will give an overview of the water resource studies currently being conducted by the USGS Pacific Islands Water Science Center in Honolulu. He will present some preliminary results of work from SERDP-funded projects on climate change impacts to DoD installations on Kwajalein (collaboration with Curt Storlazzi and the PCMSC) and Guam. Other projects underway include historic and predicted groundwater recharge studies, low-flow stream studies, island-wide groundwater models, fuel spill evaluation, impacts of using effluent as irrigation, and evaluation of inland and coastal groundwater connectivity.


Screen shot from Rob's talk.Seismic Soil Liquefaction Assessment by Shear Wave Velocity

Robert Kayen
Research Civil Engineer at USGS PCMSC, and Adjunct Professor at UCLA

Weds., January 28, 2015, 2:00 pm

Abstract: Soil liquefaction occurs when loose, saturated soil loses strength and stiffness in response to earthquake stresses and behaves like a liquid. If large earthquake stresses are rapidly applied the excess pore water pressures may rise and cause soil to lose all of strength, damaging structures built on or within it. Liquefied soil may flow like a liquid damaging large areas of habitation or industry.
This talk describes a new method to assess the seismic resistance of soil to liquefaction by measurement of the shear wave velocity (Vs) of soil layers. This study presents the results of an eleven-year international project to gather new Vs site data for 301 new liquefaction field case histories in China, Japan, Taiwan, Greece and the USA combined with previously published case histories. The method for collecting the Vs velocity profiles uses non-invasive advanced geophysical techniques based on the dispersive properties of surface waves. From these data, probabilistic correlations are presented for seismic soil liquefaction occurrence. The new dataset and probabilistic analysis also help resolve the ancillary issues of how soil texture effects liquefaction potential, and how to scale the estimated stress for earthquake duration and magnitude.


Screen shot from Karla's talk.A New Paradigm Relating Global Climate and North Pacific Intermediate Water Circulation

Karla Knudson
University of California, Santa Cruz

Weds., January 21, 2015, 2:00 pm

Abstract: North Pacific Intermediate Water (NPIW) is the primary water mass associated with Pacific meridional overturning circulation, yet little is known about how NPIW prominence and formation are linked to climate change. Models have predicted that the closure of the Bering Strait, during past glacials when relative sea level dropped at least 50 m, may have had a significant impact on NPIW. However, until now, proxy records of NPIW were limited to just the last glacial cycle and were insufficient to evaluate the links between NPIW, climate, and sea level. In this talk, I will present new results from Integrated Ocean Drilling Program Expedition 323 Site U1342 in the Bering Sea, which provide the first continuous records of NPIW over the past 35 Marine Isotope Stages (1.2 Myrs). Records of benthic foraminiferal d13C and d18O from Site U1342 indicate that increased sea ice brine formation and NPIW ventilation occurred during extreme glacials when flow through the Bering Strait was cut off. During glacial climates in which the Bering Strait was still open, the region was as weakly ventilated as during interglacials. Additionally, statistical analyses show that variations in NPIW are coherent and in-phase with variations in upper North Atlantic Deep Water, and are unrelated to changes in lower North Atlantic Deep Water. These results contradict many previous modeling studies that predict weaker NPIW influence with Bering Strait closure and an out-of-phase (see-saw) relationship between NPIW and North Atlantic Deep Water. These results offer a new paradigm relating global climate and North Pacific Ocean circulation and suggest that brine formation is a critically important process that may help to explain data-model mismatches.


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