| Title | Comparing felt intensity patterns for crustal earthquakes in the Cascadia and Chilean subduction zones, offshore British Columbia, United States, and Chile |
| Download | Downloads |
| |
| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Rutherford, J; Cassidy, J F |
| Source | Geological Survey of Canada, Open File 8912, 2022, 43 pages, https://doi.org/10.4095/330475  Open Access |
| Image |  |
| Year | 2022 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | digital; on-line |
| File format | pdf |
| Province | British Columbia |
| NTS | 92; 93A; 93B; 93C; 93D; 102; 103A; 103B; 103C |
| Area | Vancouver; Vancouver Island; Washington State; Oregon; Pacific Ocean; Canada; United States of America; Chile |
| Lat/Long WENS | -134.0000 -120.0000 53.0000 38.0000 |
| Lat/Long WENS | -84.0000 -65.0000 -16.0000 -48.0000 |
| Subjects | tectonics; geophysics; Science and Technology; Nature and Environment; Health and Safety; tectonic setting; subduction zones; downgoing slab; seismology; earthquakes; earthquake magnitudes; Cascadia
Subduction Zone; Chilean Subduction Zone; Juan de Fuca Plate; North American Plate; Pacific Plate; Nazca Plate; South American Plate; Antarctic Plate; ANSS Comprehensive Earthquake Catalog (ComCat) Documentation; Natural hazards; Methodology; Citizen
participation; Databases |
| Illustrations | block diagrams; location maps; geoscientific sketch maps; screen captures; plots; tables |
| Program | Public Safety Geoscience Assessing Earthquake Geohazards |
| Released | 2022 08 08 |
| Abstract | In this study, we utilize US Geological Survey citizen science earthquake felt intensity data to investigate whether , crustal earthquakes in the Chilean Subduction Zone show similar, "felt intensity"
distributions to events of the same magnitude and depths within the Cascadia Subduction Zone (Quitoriano & Wald, 2020; USGS Earthquake Hazards Program, 2020). In a companion article (Rutherford & Cassidy, 2022) we examine intraslab deep earthquake
intensity patterns for the Chile and Cascadia subduction zones. Building on from the intraslab companion article, the goal of this comparison is to determine whether felt intensity information from several recent large (M8-8.8) subduction earthquakes
in Chile can be applied to Cascadia (where no subduction earthquakes have been felt since 1700). This would provide a better understanding of shaking intensity patterns for future subduction earthquakes in Cascadia - critical information for
scientists, engineers, and emergency management organizations. For this research, we utilized 20 years of cataloged Did-You-Feel-It (DYFI) citizen science data from the US Geological Survey's (USGS) earthquake online catalog, the ANSS Comprehensive
Earthquake Catalog (ComCat) Documentation (USGS Earthquake Hazards Program, 2021). In total, we considered and compared intensity patterns for fourteen magnitudes from 30 earthquakes in Cascadia (ranging from magnitudes 4.5 to 7.2, the highest
magnitude event in Cascadia zone) to the intensity patterns from 114 earthquakes in Chile, with the same magnitudes as the Cascadia events (M4.5-M7.2). Our analysis involved plotting and fitting the Chile and Cascadia earthquake DYFI responses to
compare the intensity patterns for the two subduction zones. Overall, we find good agreement between felt patterns in Chile and Cascadia. For example, all plots show the expected downward trend for intensity with distance. Even distribution with
limited clustering is seen in all fourteen magnitudes, with slight intensity clustering of responses around the 30 to 600 km. This is slightly different from the intraslab pattern which demonstrated a distinct cluster at further distance from the
hypocenter, e.g., cluster at 50 to 300 km. These results provide confidence that we can use Chilean intensity data for megathrust earthquakes in Cascadia. |
| Summary | (Plain Language Summary, not published)
In this study we collect and compare felt intensity information for crustal earthquakes in the Cascadia and Chile subduction zones. We collected felt
information on earthquakes of magnitude 4.5-7.2 over the past ~20 years. By comparing these felt intensity patterns (which we found to be very similar) we have confidence in using felt intensity data for much larger subduction earthquakes recorded in
Chile to apply to the Cascadia subduction zone (where subduction earthquakes occur, but not for more than 322 years). The use of Chilean felt intensity information for better assessing the effects of subduction earthquakes in Cascadia is valuable for
engineers, scientists and emergency managers. |
| GEOSCAN ID | 330475 |
|
|