{ "accessLevel": "public", "bureauCode": [ "010:12" ], "contactPoint": { "@type": "vcard:Contact", "fn": "David R Shelly", "hasEmail": "mailto:dshelly@usgs.gov" }, "description": "A Catalog of Low-Frequency Earthquakes at the Southern Edge of Cascadia Subduction, Version 2 \nDavid R. Shelly1\n1 U.S. Geological Survey, Geological Hazards Science Center, Golden, CO 80401\nThis catalog contains 217,710 detections from 27 low-frequency earthquake (LFE) families located at the southern edge of Cascadia subduction. The included detections span from January 1, 2008, through June 30, 2026. This catalog is an updated and revised version of the previous catalog:\nShelly, D. R. (2025). A Catalog of Low-Frequency Earthquakes at the Southern Edge of Cascadia Subduction [Data set]. U.S. Geological Survey data release. https://doi.org/10.5066/P1TCKK7G\nThree aspects of the catalog are changed. First, the version 2 catalog employs waveform templates with an additional iteration of stacking compared to those published in Shelly (2025), giving higher signal-to-noise in the templates. Second, we incorporate additional stations into the templates that were only used previously for location, not detection. In combination, these changes give greater detection capability than the previous version. Finally, the detection threshold is slightly adjusted. The revised catalog applies a threshold of 8 times the daily median absolute deviation (MAD) of the correlation sum across all channels, and the mean correlation for all channels with data is required to be at least 0.11. These parameters mitigate false detections without overly muting real detections. \nOther aspects remain unchanged from Shelly (2025). The catalog integrates detections from the 27 LFE families. The estimated source locations for the 27 families remain unchanged, as does the duplicate removal process. Potential duplicate detections were removed, retaining only the detection with the highest correlation sum in any 4.0 s window.\nThe locations are given below for reference.\nDetails of the investigation are published in:\nShelly, D.R. and Materna, K.Z, Cessation of nearby low-frequency earthquake activity following the December 2024 Mw 7.0 Mendocino earthquake: the likely role of pore pressure reductions, Geophysical Research Letters, in review.\nLFE family locations have been estimated as follows, with columns of identification number, latitude (degrees), longitude (degrees), and depth (km below mean surface):\n1 40.063867 -123.597624 28.189\n2 40.069832 -123.632715 27.623\n3 40.036072 -123.684090 22.192\n4 40.070557 -123.619751 28.199\n5 40.063883 -123.593148 28.578\n6 40.063208 -123.593563 28.223\n7 40.070020 -123.630452 27.747\n8 40.088265 -123.709562 24.216\n9 40.069922 -123.621134 28.134\n10 40.069836 -123.627124 27.834\n11 40.040125 -123.675838 22.449\n12 40.068445 -123.626107 27.775\n13 40.069963 -123.623511 27.960\n14 40.036499 -123.668848 23.295\n15 40.069820 -123.632642 27.698\n16 40.064124 -123.599935 28.170\n17 40.070052 -123.620215 28.126\n18 40.067786 -123.610710 28.209\n19 40.072070 -123.686711 25.676\n20 40.064315 -123.601424 28.162\n21 40.027307 -123.606934 23.712\n22 40.073580 -123.644653 27.497\n23 40.053434 -123.556055 27.045\n24 40.064563 -123.601245 28.189\n25 40.069836 -123.619857 28.164\n26 40.072095 -123.712524 24.127\n27 40.036267 -123.532186 25.939\nThe LFE family locations may be updated in the future. Therefore they are given here separately from the catalog file.\nThe LFE catalog (LFEcat_MTJ_2018-2024.csv) fields are as follows:\nyear, month, day, hour, minute, second: Event time. Time given is template start time in UTC, starting 1 s prior to estimated S-wave arrival time at first station. Seconds are reported to 0.01s precision.\ns_of_day: Event time, given as second of the day (i.e. 0-86400 s). Time given is template start time in UTC, starting 1 s prior to estimated S-wave arrival time at first station.\nccsum: correlation sum across all stations \nthresh: initial detection threshold of 8 times the daily median absolute deviation of the correlation sum for that day\ncc_div_thr: ccsum divided by thresh\nmeancc: mean correlation among channels with data\nnchan: number of data channels existing for the event (defined by having a non-zero correlation value)\nID: full reference ID of family\nidnum: number associated with the family ID (1-27)\nNote on Family IDs:\nEach family has an associated identification code, which is a number followed by 1-2 ‘s’. The family IDs are arbitrary and are simply used as unique identifiers. Originally the numeric code was taken from the timing of the original source event. The number of ‘s’ indicates the number of iterations of stacking and cross-correlation that were applied to derive the template waveforms. The ‘z’ designator in family #17 (23012031243zs) indicates the correction of data on BK.BRIC, due to a polarity reversal in the original source event data.", "distribution": [ { "@type": "dcat:Distribution", "accessURL": "https://doi.org/10.5066/P1ZVHNGV", "description": "Landing page for access to the data", "format": "XML", "mediaType": "application/http", "title": "Digital Data" }, { "@type": "dcat:Distribution", "description": "The metadata original format", "downloadURL": "https://data.usgs.gov/datacatalog/metadata/USGS.6a5543551ba49b1af2fad2f4.xml", "format": "XML", "mediaType": "text/xml", "title": "Original Metadata" } ], "identifier": "http://datainventory.doi.gov/id/dataset/USGS_6a5543551ba49b1af2fad2f4", "keyword": [ "GHSC", "Golden", "Seismology", "USGS", "USGS:6a5543551ba49b1af2fad2f4", "earthquake", "earthquake hazards", "epicenter", "plate tectonics", "seismic" ], "modified": "2026-09-28T00:00:00Z", "publisher": { "@type": "org:Organization", "name": "U.S. Geological Survey" }, "spatial": "-123.7500, 40.0000, -123.5000, 40.1000", "theme": [ "geospatial" ], "title": "A Catalog of Low Frequency Earthquakes at the Southern Edge of Cascadia Subduction, Version 2" }