Abstract This report presents a method and Python code for detecting repeating baleen whale calls in seismic or hydrophone data. The method is designed to target calls of fin whales and blue whales common in the western North Atlantic. The Python package includes codes to download seismic data from public data centers, as well as to plot and catalog detection results. Many parameters of the detection function can be easily customized to target different populations of fin or blue whales. We applied the code to one year (2023) of data from 21 onshore seismometers in eastern Canada, including the Lower St. Lawrence Seaway, Atlantic Canada, and the eastern Arctic. We observe false detections at some stations and discuss limitations of the detection algorithm. We report the first observation of fin and blue whale calls at a seismometer onshore the eastern Gulf of St. Lawrence, as well as fin whale calls at a seismometer in Saint-George, NB near the mouth of the Bay of Fundy. Code Descriptions Two versions of the Python codes described in this report are included. "Whaleseis_2025" is the version originally submitted with the report, it was made with an slightly older version of Python3. "WhaleSeis_20260401" has had a few minor additions and edits for compatibility with newer versions of Python, it was tested using Python 3.12.12 running in Ubuntu (via WSL in Windows 11).