Ph.D. Research Seminar: Elahe Sirati

Thu, 19 Mar 2026 14:30:00 GMT

Ph.D. RESEARCH SEMINAR
DEPARTMENT OF EARTH AND ENVIRONMENTAL SCIENCES
DALHOUSIE UNIVERSITY

Elahe Sirati
Ph.D. Candidate

Title: Echoes from the Deep: Seismicity and Whale Call Analysis in Southeastern Canada Using Ocean Bottom Seismometers

Abstract: Compared to terrestrial seismometers, ocean-bottom seismometers (OBS) have a relatively brief history as a tool for monitoring natural seismicity. Modern, broadband OBS, with an ability to operate continuously up to a year or more, were first developed in the late 1990s. As major seismic zones are most often offshore, OBS have quickly become a critical data source for seismologists, including North American examples across the Cascadia and Aleutian subduction zones. In Canada, the need for modern OBS instrumentation led to the creation of the National Facility for Seismological Investigations (NFSI) in 2017, which now operates >110 OBS in multiple deployments each year. This study describes the NFSI’s long-term OBS deployments across southeastern Canada.

For our first project, we deployed 12 Güralp Aquarius broadband OBS in November 2021 in the lower Laurentian Fan Seismic Zone (∼4.5 km water depth). Eight instruments were successfully recovered with three months of usable data. After correcting clock drift using ambient-noise cross-correlation and estimating sensor orientation and tilt, we analyzed the dataset for local seismicity and biological signals. We identified 17 local earthquakes (up to ML 2.2 and depths reaching ∼39 km below the seafloor), expanding the known offshore seismicity in this region. The same dataset also revealed fin and blue whale vocalizations in the 15–25 Hz band. Using spectrogram-based detection and double-difference relocation with cross-correlation delay times, we provide an example blue whale track spanning ∼69 km over almost 24 h.

For our second project, we operated an amphibious seismic network in the Lower St. Lawrence Seaway between 2023 and 2025, integrating 8 broadband OBS, 48 short-period nodal sensors, and 4 land stations. Clock-drift analysis, noise characterization, and tilt-angle estimation showed no anomalous behavior, confirming that the OBS instruments functioned properly on the seafloor. The optimal orientation of the horizontal components was determined using ship-track noise recorded during the deployment. The seismicity catalogue derived from the combined OBS and land-station network reveals approximately twice as many earthquakes as reported in the Canadian National Earthquake Database. Ongoing analyses will focus on determining earthquake focal mechanisms and estimating stress variations with depth, as well as investigating their relationship to regional fault structures in the Lower St. Lawrence Seaway. We also observed clear detections of fin and blue whale calls at multiple OBS stations, from which a comprehensive database of calls has been compiled. Building on these detections, we aim to develop a more automated framework and construct an exhaustive catalogue of whale location tracks in the region.

Biography: Elahe Sirati is a Ph.D. candidate in the Department of Earth and Environmental Sciences at AV��ֲ�, Canada. She earned a Bachelor of Science in Physics from the University of Guilan and a Master of Science in Geophysics from the University of Tehran, Iran. Her research focuses on the analysis of seismicity and marine mammal acoustic signals recorded by ocean-bottom seismometers in offshore eastern Canada. Through her work, she has developed expertise in OBS data processing and analysis, contributing to a better understanding of offshore earthquake activity and the oceanic acoustic environment.

Elahe has participated in field deployments and recoveries of ocean-bottom and nodal seismometers along the St. Lawrence Seaway. In addition to her research, she serves as a teaching assistant for courses in applied geophysics and contributes to the academic community through service roles, including judging student presentations at the Atlantic University Geoscience Conference and participating in the Graduate Affairs Committee at AV��ֲ�. She has presented her work at several scientific conferences and has received support through awards including the J. Ewart Blanchard Memorial Scholarship and the Nedimović Family Scholarship.

Alumni-Student Mixer Night

Mon, 23 Mar 2026 20:00:00 GMT

Dear Dal alumni and friends,

Come celebrate the beginning of Spring with us. We're hosting our 4th annual student-alumni mixer at Lions Head on Monday March 23rd, 5-9pm. Free food, trivia, prizes and cash bar.

We're looking forward to catching up with all of you. See you there...

RSVP: https://forms.office.com/r/iUMVNBnd6f

ERTH6300 PhD Proposal Defences

Fri, 10 Apr 2026 12:00:00 GMT

Every year our EES graduate students formally defend their thesis proposals in April. This year it will take place on April 10.

This is your chance to glimpse the novel and world class research that is ongoing in our department. The defence is open to the public.

This year there are only 2 PhD students, so we are offering 20 minute presentations, followed by 40 minutes of questioning.

EES Honours Qualifying Exam

Fri, 10 Apr 2026 12:00:00 GMT

EES Honours Qualifying Exam

Sat, 11 Apr 2026 12:00:00 GMT

Dal Events

Ph.D. Research Seminar: Elahe Sirati

Alumni-Student Mixer Night

ERTH6300 PhD Proposal Defences

EES Honours Qualifying Exam

EES Honours Qualifying Exam