The 23 July 2010 mN 4.1 Laurier‐Station, Quebec, Earthquake: A Midcrustal Tectonic Earthquake Occurrence Unrelated to Nearby Underground Natural Gas Storage

On 23 July 2010, at 17:24 coordinated universal time (13:24 local time), a Nuttli magnitude (mN) 4.1 (Mw 3.5) earthquake occurred near Laurier‐Station, Quebec, approximately 40 km southwest of Quebec City, Quebec. The earthquake was widely felt by most people within 50 km of the epicenter and by some up to 170 km. The event had an oblique thrust mechanism at a depth of approximately 23.5 km. This focal depth indicates that the earthquake occurred in the Precambrian basement, much deeper than the 6‐km‐thick sedimentary layers at the surface. The earthquake could represent a reactivation of one of the regional normal faults imaged in the magnetic field and on reflection profiles. The immediate epicentral region is not very seismically active, and for this reason, the question arose as to whether local deep natural gas storage or shale gas hydraulic fracturing close to the area could have triggered the earthquake. The only aftershock‐recorded mN 2.1 was within 2 hours of the mainshock and took place before a field instrument was in place. Based mainly on the mid‐crustal focal depth of the earthquake, our study shows that the earthquake is not linked to the near‐surface natural gas storage or to the shale gas hydraulic fracturing in the area.