Dalhousie University project In collaboration with McGill University (Canada), GSC-Atlantic (Canada), NGU (Norway), Uppsala University (Sweden), and C-NGO (Canada)

Funded by the Marine Environmental Observation, Prediction and Response Network (NCE)

Intellectual Merit. The magnitude-7.2 ‘1929 Grand Banks Earthquake’ caused a massive submarine landslide to trigger a tsunami that inundated southern Newfoundland, killing 28 and creating widespread damage to coastal communities. It remains the deadliest earthquake (EQ) disaster in Canadian history, despite the tectonic quiescence of the Atlantic margin relative to the Pacific. The actual cause of the EQ is still debated. Further north, Baffin Island is situated in a zone of high EQ risk owing to numerous measured EQs over the last century (Fig. 1). The largest EQ on the planet above the Arctic Circle occurred here in 1933 (M7.3). While some Arctic EQs are caused by motion along well defined fault zones (e.g. the former rifted margin between Greenland and Baffin Island), many intraplate EQs may be triggered by glacially induced stresses in an interplay of tectonics, glacial loading, flexure of the lithosphere and mantle flow.

Currently in northern and eastern Canada, there is insufficient knowledge to assess the cascading EQ hazards let alone establish risk. We lack the instrumentation to precisely measure the location, depth, and magnitude of modern EQs, even in the high risk zones, and we have only recently begun to evaluate the record of pre-historic EQs and landslides. This leaves communities and infrastructure vulnerable, as was highlighted on June 17 of this (2017) year by the one of the tallest (100 m-high wave) tsunamis in recorded history that devastated the remote settlement of Nuugaatsiaq in western Greenland, directly across Baffin Bay from our field area. That tsunami, which was caused by a massive landslide that also generated a M4.1 EQ, resulted in four casualties and dozens injured out of population of 84, with half (11) of the houses in the area destroyed. Despite their relatively small sizes, these arctic hamlets are rapidly growing and require expensive infrastructure for new housing and public services, telecommunications, marine shipping, and local industries. Ulinniq is an Inuktitut word for rapid inundation of land by seawater. Inundation heights of displacement waves range from metres (Grand Banks Tsunami) to hundreds of meters (e.g., 2015 Taan Fjord in Icy Bay, Alaska event). Thus our focus is not only on the seismic hazard, but the potentially more devastating tsunami hazard. The long-term goal of ULINNIQ is to provide a comprehensive seismic and tsunamic risk analysis for Nunavut and Atlantic Canada.


Objectives, Methods, Expected Outcomes

The short-term goal of this MEOPAR proposal is to conduct an innovative and multifaceted hazard assessment of coastal NE Baffin Island and its offshore region based on four research objectives.

OBJ1: Modern seismicity of northern Baffin Bay. We will conduct critical proof-of-concept seismicity monitoring involving the acquisition of high resolution position, magnitude, and focal mechanisms for EQs in 2020 using newly created Ocean Bottom Seismometers (OBSs). OBJ1 will address the following PROBLEMS: (i) the lack of a sufficiently dense seismometer network in northeastern or Arctic Canada which lends to (ii) the poor resolution of active regional seismicity; (iii) the previous inability anywhere in the world to test hypotheses (OBJ4) regarding deglacial mantle dynamics to explain non-tectonic intraplate EQs; and (iv) the complete absence of a thorough risk assessment for EQ and tsunami hazards in this region. METHODOLOGY: In YR1, PhD1 will begin to devise the array geometry to begin the monitoring EQs with magnitude M1 and above, and to optimize the testing of glacial-triggering hypothesis (OBJ4). Twenty newly constructed OBSs (YR2) will be deployed in the late summer 2020 during opportunistic cruises with the GSC-Atlantic. YR3 will provide the first high resolution regional seismicity map for the Arctic. ANTICIPATED RESULTS: High resolution seismicity map for Baffin Bay, the first regional frequency-magnitude predictions informed with data from OBJ2, and the development of seafloor passive source seismology methodologies for applications in, for example, GIA analysis and sub-seafloor structure mapping.

OBJ2: Marine paleoseismology We will conduct the first regional paleoseismology analysis with marine sediment in the Arctic to address these PROBLEMS: (i) traditional onshore paleoseismological methods have failed because of the short preservation of strain markers in areas of active permafrost, and (ii) large MTDs with immediately overlying turbidite facies have been observed in Pond Inlet and may be seismogenic based on their extensive volumes and lack of subaerial sediment sources in the vicinity, but this needs verification. METHODOLOGY: Interpret bathymetry previously collected with a Kongsberg EM302 Multibeam Echosounder to identify landforms at the seabed including possible sediment sources, faults, and evidence of unstable seabed. Interpret 3.5 kHz sub-bottom profiler data collected in the past five years by the GSC-Atlantic and ArcticNet investigators. Seismic facies will be defined based on the amplitude, continuity, and internal configuration of reflectors and major surfaces will be defined by correlating continuous high amplitude reflectors using a consistent protocol to optimize our ability to correlate events throughout the Baffin Bay and coastal regions. Cores that have been already collected, and new opportunistic cores will be split, photographed and xradiographed using a Universal HE425 X-ray system at the GSC-A. Physical properties including compressional (p-wave) velocity, bulk density, and magnetic susceptibility, colour, shear strength using a shear vane apparatus and velocity using transducer probes and grain size with a Beckman Coulter LS230 Laser Diffraction Analyser will be measured to help interpret the geophysical facies, distinguish the sedimentary facies, and correlate similar assemblages of units from basin to basin. ANTICIPATED RESULTS: The cores and seismic reflection and multibeam data are available for Baffin Bay fjords and basins in addition to Pond Inlet. We will ascertain which MTDs in each basin are correlative, and if so, by using magnitude vs. landslide-area relationships, for the first time we will estimate the location, magnitude and timing of paleoseismic events.

OBJ3: Tsunami research. We will conduct four novel studies to establish a record of paleo-tsunamis to bridge the temporal gap and address these PROBLEMS: (i) there has never been an Arctic paleo-‘felt record’ study; (ii) despite observations of submarine and coastal landslide deposits along coastal Baffin Island, these potential tsunami triggers have been poorly studied owing to difficulties of direct dating and the expense and difficulty of access; (iii) well-preserved post-glacial raised beaches can hold excellent records of tsunamis, however in the Arctic their coarse nature and absence of back-berm ponded sediments that are not affected by cryoturbation has left any potential record untapped; and (iv) a significant submarine escarpment that may offset Quaternary marine sediments in Pond Inlet may extend onshore. METHODOLOGY: (i) Using ethically-approved methodologies previously used in the targeted communities we will collect oral testimonies of Elders who have witnessed (or have legacy knowledge of) either EQs or tsunamis over the past century. Yr1 will be used to consult with two targeted hamlets (Pond Inlet and Clyde River), arrange for local interpreters, translators, and to seek local community involvement, including, for instance, Community Hunters and Trappers Organizations, Government of Nunavut Department of Culture and Heritage, Qikiqtani Inuit Association, Ittaq Heritage and Research Society, Nunavut Research Institute, and researchers at Arctic College, Nunavut Tunngavik Inc., and the Nunavut Planning Commission. The interviews will be collected in 2019, in time to inform OBJ4. (ii) We will date carefully targeted ancient large rock avalanches and slips surfaces on fjord walls above gradually slipping large blocks. Detailed mapping to establish the location of incipient or actively sliding blocks will be carried out. The dating will be accomplished at Dalhousie using cosmogenic isotopes 10Be and 14C that are produced in quartz minerals exposed to cosmic rays after the complete or gradual slope failure. (iii) We will test the hypothesis that regional anomalies in the density of cultural habitation features (paleodemography) on Holocene raised beaches which cannot be readily explained by climate change, are indicative of destruction by tsunami (one particular regional anomaly corresponds to a tentatively dated 3-ka MTD observed in Pond Inlet). (iv) We will seek to find the inferred active fault near the Hamlet of Pond Inlet, and attempt to establish its kinematics and strain history to calculate the recurrence interval for given magnitudes. If correlable with the submarine escarpment, we will infer the potential for vertical seafloor offsets that may trigger a tsunami. ANTICIPATED RESULTS: All four sub-projects will contribute the first tsunami recurrence interval in Arctic Canada, which is needed to eventually establish risk along northeastern Baffin Island.

OBJ4: Testing the deglacial triggering hypothesis Owing to past and extant glacier loads that depress the Earth’s lithosphere, certain patterns in the deformation of the mantle and lithosphere occur under and around the former ice sheets. During and after melting, the mantle slowly readjusts to an equilibrium shape by viscous flow. This typically leads to uplift in formerly-glaciated areas and subsidence in their surroundings. The whole process is known as Glacial Isostatic Adjustment (GIA), and describes the response of the solid Earth to mass redistribution during a glacial cycle. The deformation of the lithosphere also leads to horizontal stresses, which accompany the vertical stresses induced by the glaciers themselves. PROBLEMS (i) As the deformation process caused by the viscoelastic nature of the mantle is slower than the rate of melting of the ice sheets, horizontal stresses induced by loading of ice sheets remain for millennia after ice load removal, making recurrence intervals long and difficult to predict. (ii) These additional stresses change the stress conditions in a region, and stable faults, i.e. formerly-quiet planes of weakness, can be reactivated in places that would not be predicted without geodynamical modeling. METHODOLOGY: To understand the recent and past seismicity within Baffin Bay, we will create a model of Greenland and North America that computes the process of GIA and the accompanying stress changes. The model will be informed with deglacial and GIA data for the region and with the benefit of the paleo- and modern seismology (OBJs1,2,3). In YR1 and YR2 we will begin to collect the boundary conditions and constrain the controlling factors in the models, and in a feedback manner, devise an optimal design for the high resolution OBS array. In YR3, we will achieve a very early version of GIA model, to begin to test if any patterns of modern and paleo-seismicity correspond to computed stress fields related to non-tectonic GIA forces in the northern Baffin Bay region. ANTICIPATED RESULTS: We envision this as the significant beginning of a ten-year effort by the ULINNIQ team, which will ultimately provide the mantle-lithosphere geodynamical model for Baffin Bay and the Labrador Sea to help predict magnitude and locations of future seismicity.

Broader Impacts. The majority of residents and infrastructure in Nunavut communities is situated well within reach of tsunamis. Atlantic and Arctic Canada lacks the scientific knowledge required to inform policies for buiding, landuse, and evacuation, yet it is in a tsunami-prone region (as witnessed by the recent deadly tsunami in Greenland) and a high seismicity region. Our project combines modern seismology studies, paleoseismological and geochronological work, as well as oral testimonies of Elders, to improved predictions of earthquake recurrence rates and detection and characterization of tsunamis.