Data from: Catalog of non-seismic short duration events offshore cascadia
Data files
Feb 13, 2025 version files 733.42 MB
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CascadiaShortDurationEvents.zip
733.42 MB
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README.md
4.93 KB
Abstract
Ocean-bottom seismometers (OBS) often record non-earthquake signals termed short-duration events (SDEs) that are typically recorded on one station with durations of ~1 s and frequencies between 4-30 Hz. Their origin has been attributed to animals bumping the sensor and a variety of physical mechanisms, including the passage of methane bubbles through sediments and across the seafloor. We analyzed records from a subset of OBSs deployed on the Cascadia margin and Juan de Fuca plate as part of the Cascadia Initiative experiment and cabled OBSs from the Ocean Observatories Initiative Regional Cabled Array for the occurrence and characteristics of SDEs. SDEs are observed on all OBSs at rates that vary by over two orders of magnitude. This data set comprises a catalog of short duration from the OBS analyzed along with the Python code used to analyse the data, a list of stations and the time intervals analyzed, and ocean tide height predictions at each site.
This repository contains information related to the manuscript "Non-Seismic Short Duration Events Offshore Cascadia: Characteristics and Potential Origin" by Leo M. F. MacLeod and William S.D. Wilcock, in review at the journal “Seismological Research Letters”.
Summary of Files
README.md – Description of repository contents (this file)
CascadiaShortDurationEvents.zip - A zip file containing the following directories and files:
Catalogue_SDE.py – Python code used for generating the station event catalogues used in this study.
ListofStations.csv – Comma separated variable file with details on each station.
TideHeightData – Directory containing data files of tidal height for each station used.
DataCatalogue – Directory containing comma separated variable files for each station with data for each short duration event detected.
File Details
**Catalogue_SDE.py **
A Python code used to generate the data used in the analysis of this study that can be found in the “DataCatalogue” directory. This code detects short duration events for a given ocean bottom seismometer station and range of times. Data is pulled from the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (now the Earthscope Consortium Seismological Facility for the Advancement of Geoscience (SAGE) Data Services). Parameters for the station identifier and time range can be changed. Code runs in intervals of one hour and the start times can be modified to restart from a specific time if a crash occurs. Data is saved for each station catalogue as a comma separated variable (csv) file. This Python code uses data from ListofStations.csv with data on each station used and the directory “TideHeightData” containing files on tidal height by station.
**ListofStations.csv **
A comma separated variable file with information about the stations that is needed to run the Python code Catalogue_SDE.py. It has eight columns of data:
Column 1 is the station name.
Column 2 is the network code for the station. This is either “7D” for Cascadia Initiative Community Experiment or “OO” for Ocean Observatories Initiative Regional Cabled Array.
Column 3 is the station depth in meters.
Column 4 is the station latitude in decimal degrees north.
Column 5 is the station longitude in decimal degrees east.
Column 6 is the start time of the station in Unix epoch.
Column 7 is the end time of the station in Unix epoch.
Column 8 is the amplitude that an event must reach to be counted as a short duration event as opposed to background noise.
TideHeightData
A directory that contains one data file for each station analyzed with the station name as the first 4 or 5 characters before the underscore. These files are used to add the tidal height in column 13 for each csv file in the “DataCatalogue” directory. Each file contains two columns:
Column 1 is the time in Unix epoch.
Column 2 is the tidal height in meters obtained from the Oregon State University TPXO tidal model as implemented in SPOTL (Agnew, D. C. (2013) Some Programs for Ocean-Tide Loading, Program Versions 3.3.0.2, Scripps Institution of Oceanography, Technical Report, https://igppweb.ucsd.edu/~agnew/Spotl/spotlman.pdf).
DataCatalogue
A directory that contains one csv file for each station analyzed with the station name as the first 4 or 5 characters before the underscore. Each row in the file contains data for one detected short duration event. Details on the math for calculating the characteristics of each event are included in the Materials and Methods section of the manuscript. Each file contains 13 columns:
Column 1 is the station name.
Column 2 is the start time of the detected event in Unix epoch.
Column 3 is the end time of the detected event in Unix epoch.
Column 4 is the total duration of the event in seconds.
Column 5 is the number of peaks counted in the event.
Column 6 is the maximum amplitude digital units of the downloaded data after filtering with a 5-12 Hz Butterworth bandpass filter.
Column 7 is greatest change in amplitudes between peaks in multi-peak events in digital units of the downloaded data after filtering with a 5-12 Hz Butterworth bandpass filter. A value of 0 means there was only one peak so a distance between peaks is inapplicable.
Column 8 is the mean energy weighted time of the event (equation 2 in the manuscript).
Column 9 is the energy weighted duration of the event in seconds (equation 1 in the manuscript).
Column 10 is the average frequency of the event in Hz (equation 3 in the manuscript).
Column 11 is the bandwidth of the event in Hz (equation 4 in the manuscript).
Column 12 is the elevation angle of the sun in degrees above the horizon.
Column 13 is the tide height during the event in meters.
The data set was collected with ocean bottom seismometers deployed as part of the Cascadia Initiative Experiment (Toomey et al., 2014)and as part of the Ocean Observatories Initiative Regional Cabled Array (Smith et al.). Short duration events (SDEs) were detected by first filtering the seismic records with a 5-12 Hz bandpass filter and then using a recursive short term/long term RMS amplitude detector with a short- and long-term durations of 0.25 s and 30 s, respectively, and a trigger ratio of 4 (Withers et al., 1998). Various parameters were then determined for each short duration event (SDE) as described in the README file accompanying this data set
Smith, L. M., Barth, J. A., Kelley, D. S., Plueddemann, A., Rodero, I., Ulses, G. A., ... & Weller, R. (2018). The ocean observatories initiative. Oceanography, 31(1), 16-35.
Toomey, D. R., Allen, R. M., Barclay, A. H., Bell, S. W., Bromirski, P. D., Carlson, R. L., ... & Wilcock, W. S. (2014). The Cascadia Initiative: A sea change in seismological studies of subduction zones. Oceanography, 27(2), 138-150.
Withers, M., Aster, R., Young, C., Beiriger, J., Harris, M., Moore, S., & Trujillo, J. (1998). A comparison of select trigger algorithms for automated global seismic phase and event detection. Bulletin of the Seismological Society of America, 88(1), 95-106.