(Earthquake) Magnitude 4.9 - VANCOUVER ISLAND, CANADA REGION

USGS Earthquake Hazards ^ | March 1, 2005

[bd476]

Magnitude 4.9 - VANCOUVER ISLAND, CANADA REGION
2005 March 1 21:34:30 UTC

Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver

A light earthquake occurred at 21:34:30 (UTC) on Tuesday, March 1, 2005. The magnitude 4.9 event has been located in the VANCOUVER ISLAND, CANADA REGION. (This event has been reviewed by a seismologist.)

Magnitude	4.9
Date-Time	Tuesday, March 1, 2005 at 21:34:30 (UTC) = Coordinated Universal Time Tuesday, March 1, 2005 at 1:34:30 PM = local time at epicenter
Location	48.304°N, 128.845°W
Depth	10 km (6.2 miles) set by location program
Region	VANCOUVER ISLAND, CANADA REGION
Distances	282 km (175 miles) SSW (201°) from Port Hardy, BC, Canada 313 km (194 miles) W (270°) from Neah Bay, WA 323 km (201 miles) SW (236°) from Campbell River, British Columbia, Canada 403 km (251 miles) W (269°) from Saanich, British Columbia, Canada 432 km (269 miles) WSW (258°) from Vancouver, British Columbia, Canada
Location Uncertainty	horizontal +/- 6.8 km (4.2 miles); depth fixed by location program
Parameters	Nst= 87, Nph= 87, Dmin=353.7 km, Rmss=1.05 sec, Gp=158°, M-type=body magnitude (Mb), Version=6
Source	USGS NEIC (WDCS-D)
Event ID	usvcbg

[bd476]

Historical USGS Moment Tensor Solutions

[KC Burke]

about the sixth of that magnitude there in the last 48 hours

[bd476]

Ping.

[Bahbah]

about the sixth of that magnitude there in the last 48 hours

Oh, really. I guess that's a good thing though since it's not all being saved up for a big one.

[Strategerist]

There was a very similar swarm (even more quakes) in the same location in 2001.

It's at the ridge and transform faults at the junction of the Pacific Plate and the Juan de Fuca Plate and the Explorer microplate....very complex region.

Possibly associated with volcanism on the ridge. No particular implications for any sort of big subduction quake, really.

[djf]

Yup. I haven't felt any of the shakin, though.

4.9 2005/03/01 21:34:30 48.304 -128.845 10.0 313 km (194 mi) W of Neah Bay, WA
4.4 2005/03/01 16:08:32 48.248 -128.735 10.0 305 km (189 mi) W of Neah Bay, WA
4.8 2005/02/28 13:50:25 48.321 -128.777 10.0 308 km (191 mi) W of Neah Bay, WA
4.5 2005/02/28 13:23:50 48.380 -128.446 10.0 283 km (176 mi) W of Neah Bay, WA
4.9 2005/02/28 12:49:24 48.314 -128.823 10.0 311 km (193 mi) W of Neah Bay, WA
3.7 2005/02/27 20:46:43 48.278 -127.682 10.0 227 km (141 mi) W of Neah Bay, WA

[bd476]

[KC Burke]

yes, when I saw this thread I rememebered noting this small swarm when I had checked Iris earlier in the afternoon.

I don't think it points to anything -- but it does mean some released energy is getting closer to California, a California has been very seismically quiet for the last couple of months -- almost strangely quiet

[Quix]

Thanks much.

Something in the earth is building for another emphatic exclamation point. I still think it will be on the Pacific ring of fire somewhere.

Evidently it was NOT within 60 days of the Sumatran quake. Glad of that. I knew it was a super subtle thought/feeling--too subtle to put any stock in--though I still 51%+ expected something anyway. The next month or 3 should be interesting.

What's the count to for 5.X and above since the Sumatran quake? It must be above 115.

[bd476]

Some perspective:

Last 8 to 30 Days of Earthquake Activity

[bonfire]

Couple of small earthquakes on the shores of Western Lake Erie the past few weeks.

[djf]

Yesterday was the 4 yr anniversary of the Nisqually quake. That one was 6.8 or 7.2 depending on who you ask. I wasn't home when it hit, but was amazed to not find a single thing out of order.

Subduction type quakes tend to have alot more up and down motion, rather than the horizontal, slip type motion of say the San Andreas fault.

A quake that big in the Bay area would be devastating.

[Strategerist]

Nisqually quake was deep. It wasn't really subduction vs. other types of quakes, (there are shallow subduction quakes, like Sumatra) but the absence of really severe damage was solely due to depth.

[Ernest_at_the_Beach]

[djf]

There were people in downtown Seattle, further from the epicenter than me, who reported that it seemed the whole building moved up and down a foot or so a couple times, then quieted down.

Structurally, buildings can take that kind of motion much better than a strong lateral shift.

[BreitbartSentMe]

Hmmm, I'll have to call my sister on Victoria and see if they felt anything.

[Strategerist]

Structurally, buildings can take that kind of motion much better than a strong lateral shift.

Incorrect.

Look at Northridge. Strongest ground accelerations ever instrumentally recorded. It was a thrust quake and the primary motion was up and down.

Smaller than the Nisqually quake magnitude wise and did 20+ billion dollars of damage.

The only saving grace of the Nisqually quake was depth. Had it been as shallow as Northridge, with the same motions, you would have had hundreds killed and tens of billions of dollars of damage.

[bd476]

Magnitude 6.8 WASHINGTON
2001 February 28 18:54:32 UTC

Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver

	Date-Time	2001 02 28 18:54:32 UTC
	Location	47.14N 122.72W
	Depth	52.0 kilometers
	Magnitude	6.8
	Region	WASHINGTON
	Reference
	Source	USGS NEIC

The preliminary mechanism for this earthquake is tensional (normal) faulting in the subducting (downgoing) Juan de Fuca Plate, caused by bending of the plate. Damage and injuries have occurred in the Olympia-Seattle area. This earthquake is located in the same general area as a magnitude 7.1 earthquake on April 13, 1949. The location for this earthquake was furnished by the Geophysics Program, University of Washington, Seattle.

About 400 people injured and major damage in the Seattle-Tacoma- Olympia area. Maximum intensity (VIII) in the Capitol Hill area of Olympia and in the Pioneer Square area south of downtown Seattle. Preliminary estimates of damage are between 1 and 4 billion U.S. dollars. Felt from central Oregon to southern British Columbia and as far east as northwestern Montana. The maximum recorded acceleration was 0.3g at Seward Park. Landslides occurred in the Tacoma area and near Renton. Liquefaction and sand blows occurred in parts of Olympia and South Seattle.

No aftershocks were recorded by the University of Washington network in the first 6 hours following the magnitude 6.8 main shock. In a typical aftershock sequence, the highest rate of aftershock activity occurs during this period. Earthquakes of comparable magnitude with nearby epicenters and similar depths occurred in 1949 and 1965. The 1949 earthquake had only one aftershock in the following six months, and little aftershock activity was observed following the 1965 earthquake. On the basis of this information, we do not expect significant aftershocks from today's earthquake. The depths (50-70 km) of these three earthquakes may be a factor in their low aftershock productivity. Shallow (less than 20 km) mainshocks are more likely to have energetic aftershock sequences.

[Strategerist]

http://www.scec.org/news/01news/feature010313.html

"Much of the difference in the total damage caused by the Nisqually and the Northridge earthquakes can be attributed to the Nisqually earthquake's location -- not that of its epicenter, but rather, the depth of its hypocenter. The Northridge earthquake had a hypocentral depth of 18 kilometers (11 miles), deep for a California earthquake, but considered shallow compared to other regions. The Nisqually earthquake had a depth of some 52 kilometers (33 miles), meaning that no building experienced greater shaking than would be expected at a distance of 52 kilometers from a magnitude 6.8 earthquake. That may seem to be an obvious statement, but earthquake depth is often entirely overlooked in reports of an earthquake's effects; conversely, no one would be surprised if it were reported that a town at a distance of 18 kilometers from an earthquake's epicenter suffered greater losses than one located 52 kilometers away from the epicenter."