• Medientyp: E-Book; Bericht
  • Titel: 2012 Haida Gwaii Mw 7.7 Earthquake Response - Ocean Bottom Seismometer Relocation and Geophone Orientation Analysis and Quality Control of Wide-Angle P-wave Refraction Data
  • Beteiligte: Riedel, Michael [Verfasser:in]; Côté, M. M. [Verfasser:in]; Neelands, P. J. [Verfasser:in]; Middleton, G. [Verfasser:in]; Standen, G. [Verfasser:in]; Iuliucci, R. [Verfasser:in]; Ulmi, M. [Verfasser:in]; Stacey, C. D. [Verfasser:in]; Murphy, R. [Verfasser:in]; Manning, D. [Verfasser:in]; Brillon, C. [Verfasser:in]; Spence, G. D. [Verfasser:in]
  • Erschienen: OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel), 2014
  • Umfang: text
  • Sprache: Englisch
  • DOI: https://doi.org/10.4095/295551
  • Entstehung:
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  • Beschreibung: Canada's second largest instrumentally recorded earthquake occurred on October 27th, 2012, off the west coast of Moresby Island, Haida Gwaii. Analysis of seismic waveforms and the pattern of aftershocks indicate that it was a thrust earthquake with a magnitude of Mw = 7.7. To accurately locate earthquakes, recording stations need to be positioned such that they surround the epicenter and the sound speed at which seismic waves travel through the earth's crust must be known. The land stations on Haida Gwaii are all to the east of the aftershock sequence, thus making these offshore earthquake locations uncertain and making depths for those events almost impossible to calculate accurately. Only sparse information from seismic refraction work conducted in the early 1980ies on the offshore velocity structure around the epicenter is known. Therefore, a series of 14 ocean bottom seismometers (OBS) were deployed for the duration of 1 month between December 6, 2012 and January 5, 2013 to record a portion of the aftershock sequence. An active source seismic program was conducted in January 2013 prior to the OBS recovery to acquire information on the sediment- and crustal structures to aid in the earthquake location analyses. However, the initial refraction data were not recorded on any of the 14 OBS as the batteries on all of the OBS stations had drained by the time of the survey. An extra set of six OBS was re-deployed and a total of four single-channel seismic profiles were acquired across these six OBS stations for a smaller-scale detailed refraction velocity experiment. Using the active source seismic data, each of the six OBS of the second deployment were re-located on the ocean floor, which is a critical pre-requisite for any velocity analysis. The OBS instruments drifted on average by 200m to the NW of the deployment drop-position. New offset information for the relocated OBS stations were calculated, and used for an initial exemplary but non-ray-tracing based 1D refraction velocity analysis on selected OBS stations ...
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