B.C. earthquakes could be foreshocks leading to a large one, Canada

B.C. earthquakes could be foreshocks leading to a large one, Canada

A swarm of earthquakes that started in December 2014 along the border of the Juan de Fuca and North American plates, northwest of Vancouver Island, British Columbia - Canada, continued into 2015 with two moderately strong earthquakes measuring M4.5 and 5.2 on the Richter scale. 

According to John Clague, a Simon Fraser University professor, a larger earthquake off Vancouver Island’s shore could be around the corner.

The swarm started on December 17, 2014 with M3.8 at a depth of 10 km, 195 km west of Port Hardy, according to data collected by Earthquake Canada.

By January 5, 2015 they registered a total of 39 moderate to strong earthquakes in the same region, with the strongest one being 10-km deep, M5.4 on January 2, 2015. See the map and a complete list of quakes below.

“It is an earthquake-prone territory, but this is a fairly large number of earthquakes to have in such a short period. It’s possible we won’t know until time passes that these could be foreshocks of a larger earthquake in the same area, something in the magnitude six or seven range,” Clague said

Although the slew of tremors have been frequent, there’s no direct link for it to trigger the “big one” further south on the Juan de Fuca plate and the Cascadia Subduction Zone, he explained and added that while it is normal for a cluster of earthquakes to hit along the border of the Juan de Fuca and North American plates, it’s unlikely any damage will result from a seven-magnitude quake, as long as it remains offshore. 

There is good evidence that the Juan de Fuca and North America plates are currently locked together, causing strain to build up in the earth's crust. It is this squeezing of the crust that causes the 300 or so small earthquakes that are located in southwestern British Columbia each year, and the less-frequent, once per decade, on average, damaging crustal earthquakes (e.g., a magnitude 7.3 earthquake on central Vancouver Island in 1946).

At some time in the future, these plates will snap loose, generating a huge offshore "subduction" earthquake - one similar to the 1964 M=9.2 Alaska earthquake, or the 1960 M=9.5 Chile earthquake. Current crustal deformation measurements in this area provide evidence for this model. Geological evidence also indicates that huge subduction earthquakes have struck this coast every 300 - 800 years. (Earthquakes Canada)

DateTime (UTC)DepthMagRegion
2015/01/0401:49:5510.04.5214 km W of Pt. Hardy,BC
2015/01/0215:00:2910.03.4213 km W of Pt. Hardy,BC
2015/01/0214:56:5510.03.4217 km W of Pt. Hardy,BC
2015/01/0214:37:5510.03.1215 km W of Pt. Hardy,BC
2015/01/0210:15:3310.05.4217 km W of Pt. Hardy,BC
2014/12/3105:38:5110.02.7217 km W of Pt. Hardy,BC
2014/12/3104:35:3110.02.8218 km W of Pt. Hardy,BC
2014/12/3019:28:1139.52.0105 km SSW of Pt. Hardy,BC
2014/12/2601:13:2210.02.5118 km SSW of Pt. Hardy,BC
2014/12/2501:26:4610.03.3213 km W of Pt. Hardy,BC
2014/12/2413:07:3910.03.9215 km W of Pt. Hardy,BC
2014/12/2323:49:5910.03.7220 km W of Pt. Hardy,BC
2014/12/2323:42:1510.03.7222 km W of Pt. Hardy,BC
2014/12/2318:20:373.72.185 km SW of Pt. Hardy,BC
2014/12/2306:58:2110.03.5211 km W of Pt. Hardy,BC
2014/12/2303:00:0310.03.6215 km W of Pt. Hardy,BC
2014/12/2301:17:5310.03.8216 km W of Pt. Hardy,BC
2014/12/2301:16:2110.03.4221 km W of Pt. Hardy,BC
2014/12/2221:01:0310.04.4217 km W of Pt. Hardy,BC
2014/12/2206:51:3710.04.5219 km W of Pt. Hardy,BC
2014/12/2110:45:4410.04.6213 km W of Pt. Hardy,BC
2014/12/2110:19:4510.04.3217 km W of Pt. Hardy,BC
2014/12/2109:40:4510.05.1220 km W of Pt. Hardy,BC
2014/12/2107:35:4810.04.0216 km W of Pt. Hardy,BC
2014/12/2105:19:4010.04.1216 km W of Pt. Hardy,BC
2014/12/2103:59:5010.03.8215 km W of Pt. Hardy,BC
2014/12/2102:57:3510.05.0219 km W of Pt. Hardy,BC
2014/12/2022:54:2810.04.6216 km W of Pt. Hardy,BC
2014/12/2021:36:3210.04.2216 km W of Pt. Hardy,BC
2014/12/2017:45:2310.03.7213 km W of Pt. Hardy,BC
2014/12/1903:17:5310.03.9206 km W of Pt. Hardy,BC
2014/12/1902:25:3310.03.6211 km W of Pt. Hardy,BC
2014/12/1900:36:2410.03.6203 km W of Pt. Hardy,BC
2014/12/1822:31:5910.03.7228 km W of Pt. Hardy,BC
2014/12/1810:46:1510.03.4193 km W of Pt. Hardy,BC
2014/12/1808:34:0110.03.5209 km W of Pt. Hardy,BC
2014/12/1707:44:4310.03.2185 km WSW of Pt. Hardy,BC
2014/12/1706:33:2410.03.3186 km WSW of Pt. Hardy,BC
2014/12/1701:27:1410.03.8195 km W of Pt. Hardy,BC

Data by Earthquake Canada. Last updated: 09:30 UTC on Monday, January 5, 2015.

Featured image credit: Earthquake Canada

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