Hydrology in submarine subduction zones - from sampling to quantifying fault slip using Geochemistry

Marine hydrologists and geochemists collect fluid samples in submarine subduction zones through ocean drilling, remotely operated vehicles, and benthic fluid samplers. Analyzing the chemical compositions of the fluid allows us to understand where the deep fluid comes from, what reactions are happening deep within subduction zones, and the activities of deep microorganisms below the seafloor. Fluid chemistry also allows us to quantify transient events that shape subduction zone behavior. This seminar will introduce the general tools for investigating fluid flow below the seafloor, as well as Man-Yin Tsang’s recent project offshore New Zealand, which links fluid chemistry and fault slip research.

The outer forearc of the northern Hikurangi subduction zone, New Zealand, hosts diverse fault slip modes, including slow slip events (SSEs) and tsunamigenic earthquakes. Splay faults, which branch from the megathrust at steeper angles, can slip during earthquakes and generate large tsunamis. While such slip along splay faults is evident in some subduction zones, quantitative knowledge of their activity, as well as their occurrence in subduction zones with diverse fault slip modes, remains limited. The Papaku Fault of the Hikurangi subduction zone, a major splay fault landward of the deformation front, has a large offset and soles into the megathrust near the SSE source area. Ocean drilling penetrated the Papaku Fault at ~300 metres below the seafloor, revealing that it formed from the overthrusting of a consolidated hanging wall onto a previously unburied footwall.

Pore water solute profiles from the sediment drill cores show a repeated early diagenetic sequence in the footwall, confirming overthrusting of ancient seafloor sediments. Post-burial reactions and solute diffusion across the fault produced non-steady-state solute profiles. Using bromide, ammonium and chloride profiles, we can estimate when overthrusting started, the contemporary slip rate of the splay fault, and the contribution of the splay fault to the overall plate motion. These findings demonstrate that plate motion is partitioned between the megathrust and splay faults, emphasizing the role of splay faults in regional hazard assessments.

Date: Tuesday, January 20
Time: 3:30 - 4:30 PM
Location: Kirk Hall, Room 146

Speakers:

Centre for Hydrology Research Update

Join us for an update on the Centre for Hydrology's activities and research, presented by Director John Pomeroy and Associate Directors, Cherie Westbrook and Warren Helgason. This session is open to hydrology faculty, staff, students, and anyone interested in learning more about our work and future directions.

Date: Tuesday, September 23
Time: 3:30 - 4:30 PM
Location: Kirk Hall, Room 146

Speakers:

Design floods in a changing Earth: practices, challenges, and pathways forward

Design floods are central to how we plan, design, and adapt to future hydroclimates. Yet, we should improve the way we estimate them. In this talk, I will discuss how practices across Canada vary widely, often with limited transparency and little consideration of nonstationarity or other Earth system complexities. These challenges matter because they shape how we prepare for climate change. I will also highlight two recent advances that point to pathways forward: (a) new frameworks for flood frequency analysis that make nonstationary modelling more accessible, systematic, and reproducible, and (b) novel bias-correction methods that improve how climate model projections of extreme events are adjusted for local-scale practical use, explicitly accounting for continuous climate change. Together, these perspectives point toward more transparent, robust, and realistic approaches to design flood estimation. Achieving this vision, however, will require continued research and stronger collaboration among practitioners, researchers, and governments.

Date: Monday, October 20
Time: 3:30 - 4:30 PM
Location: Kirk Hall, Room 146

Speakers:

Lakes, Change, and Adaptation in the Prairies: How Hydrology can help Limnology

The Prairies are a constantly changing environment, subject to multiple stressors impacting water security. Water quality in the region is often poor, impacting multiple water uses, including water treatment, recreational uses and cultural uses. Using lessons from a long-term partnership on water treatment, this seminar will address about how water quality has been changing and highlight important hydrological and/or agricultural questions related to future change. The discussion will include the potential for further collaborative water research on campus that spans multiple disciplines, focussing on societal needs for adaptation to water quality stressors.

Date: Monday, November 17
Time: 3:30 - 4:30 PM
Location: Kirk Hall, Room 146

Speakers: