{"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 \nDavid R. Shelly1\n1 U.S. Geological Survey, Geological Hazards Science Center, Golden, CO 80401\nThis catalog contains 61,441 detections from 27 low-frequency earthquake (LFE) families located in an isolated zone offset to the west from the southern edge of the main band of Cascadia tremor.  The included detections span from January 1, 2018, through November 30, 2024. Details of the investigation are published in:\nShelly, D. R., Goldberg, D. E., Wech, A. G., & Thomas, A. M. (2025). A northeast-dipping zone of low-frequency earthquakes at the southern edge of Cascadia subduction. Geophysical Research Letters, 52, e2025GL116116. https://doi.org/10.1029/2025GL116116\nAs presented here, the catalog integrates detections from the 27 LFE families. A threshold of 9 times the daily median absolute deviation (MAD) of the correlation sum across all channels is applied.  Additionally, we require the mean correlation for all channels with data to be at least 0.12.  This provides more robust detection than the initially applied threshold of 8 times MAD. Potential duplicate detections were removed, retaining only the detection with the highest correlation sum in any 4.0 s window. Please see publication above for further details.\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 \u2018s\u2019. The family IDs are almost meaningless and are simply used as unique identifiers. Originally the numeric code was taken from the timing of the original source event. The number of \u2018s\u2019 indicates the number of iterations of stacking and cross-correlation that were applied to derive the template waveforms. The \u2018z\u2019 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/P1TCKK7G", "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.68278bb3d4be02693eeab6f4.xml", "format": "XML", "mediaType": "text/xml", "title": "Original Metadata"}], "identifier": "http://datainventory.doi.gov/id/dataset/USGS_68278bb3d4be02693eeab6f4", "keyword": ["GHSC", "Golden", "USGS", "USGS:68278bb3d4be02693eeab6f4", "earthquake", "earthquake hazards", "epicenter", "plate tectonics", "seismic"], "modified": "2025-09-30T00:00:00Z", "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"}