Juan de Fuca Plate Activity

[dgavin]

No additiona quakes list week, other then the noted 2.

A 3.1 EQ this moring just off the coast west of Newport. Same region as last weeks events.

[dgavin]

A 4.1 EQ 2am this morning on the southern area of the Rift Zone, it Doesn't appear to be volcanic.

[dgavin]

This moring starting just after 1:30am PDT, a micro-swarm of Earthquakes occured on Jaun De Fuca plate along the Subduction region just off the coast of Newport Oregon. Quake's registered in at 3.2, 3.7, then 3.1, at about 30km depth, then the swarm immediately stoped.

I can't really say what this is, as I haven't seen such a small number of quakes in a swarm before, with magnitudes over 1.8. This swarm is around the estimated depth of the Jaun-der-Fuca/Pacific junction area however, so I suspect these were not Strike/Slip quakes, but Lateral/Slip quakes. No movement solutions were posted for them yet, so thats only a guess.

[Trebuchet]

As long as they don't send a major tsunami up the actual Strait of Juan de Fuca, I'm good with that. I spend way too much time looking out at it and wouldn't want any unpleasantries.

[dgavin]

Another 1.9 over the weekend, and just a few (11:04am PDT) minutes ago, an unspecified Mag quake that showed on almost all Oregon siemographs, with Reedssport being the closest one to the quake. This isn't even posted to the auto events yet. Soon as i find out mroe i'll post a followup.

[dgavin]

And just a few (11:04am PDT) minutes ago, an unspecified Mag quake that showed on almost all Oregon siemographs, with Reedssport being the closest one to the quake. This isn't even posted to the auto events yet. Soon as i find out mroe i'll post a followup.

It was a preliminary 6.0 quake 500 miles offshore of Acapulco, Mexico, on the Pacific Rift, 9.9 km deep. Scratch this one of the Jaun-de-Fuca list

[dgavin]

Not to be left out, the was a 4.4 mag quake last night on the Juan De Fuca ridge, due west of Coos Bay Oregon.

[Gillianren]

Juan. And Coos Bay.

[dgavin]

2 aftershocks so far from the 4.4 event, both registering 2.1 magnitude.

[dgavin]

There was a 5.9 Quake along the Juan-de-Fuca Ridge (Slip) area, off the Oregon coast, west of Brandon, OR, about 2 hours ago.

This puts the amount of strong quakes at 1 over the normal yearly average. I have no additional comments yet on that little fact.

[Trebuchet]

I think that would be Bandon, not Brandon. Home of one of my favorite little lighthouses. Which I see they've at least partially painted since we were there.

[dgavin]

So far 3 aftershocks to the 5.9 Quake, off the coast of Bandon Oregon, last weeks aftershocks were 2.6 and 2.8. This mornings was a 3.4.

[dgavin]

2 More quakes since yesterdays report. Both along the subduction region this time, a 4.1 Mag near Eureka, CA and a 2.8 Mag near Newport, OR.

[dgavin]

4.1 Mag Yesterday near northern edge offshore of Canada

[dgavin]

Busy week for Juan de Fuca plate.

The 4.1 in prior post the offshore Canada quake was updated to a 4.4, and there were 3 subsequent evens in same region, 3.9, 4.0 and 4.4 magnitudes.

At the otherside of the plate off shore of California, there was a 2.5, 3.0 and a 3.8 mag.

[dgavin]

So far since last report

2 more quakes off shore of Canada, in same region as others, a 4.5 mag and a 4.0 Mag.

Off shore of california another 3.8 mag quake.

[dgavin]

After quite some time of quietness, there have been four events this week. A 5.1 and a 5.2 earthquake along the southern plate edge, off of california's coast, and a 4.1 and a 4.2 in the mid plate slip flault zone, off the oregon coast.

[dgavin]

Starting on the 29th, there has been what now qualifies as a small earthquake swarm, on the subduction region about 20-30km off shore of Gold Beach, Oregon

2.9 34km SW of Gold Beach, Oregon 2012-08-02 00:00:44 42.204°N 124.746°W 21.9
2.6 29km SW of Gold Beach, Oregon 2012-08-01 10:59:38 42.235°N 124.693°W 0.0
2.8 31km SW of Gold Beach, Oregon 2012-08-01 07:15:17 42.228°N 124.718°W 4.8
2.2 29km SW of Gold Beach, Oregon 2012-08-01 04:30:45 42.210°N 124.665°W 0.0
2.1 26km SW of Gold Beach, Oregon 2012-08-01 03:03:05 42.223°N 124.627°W 0.1
1.9 28km SW of Gold Beach, Oregon 2012-08-01 02:15:17 42.196°N 124.627°W 18.3
2.2 26km SW of Gold Beach, Oregon 2012-08-01 01:00:50 42.241°N 124.649°W 0.0
2.5 27km SW of Gold Beach, Oregon 2012-08-01 00:34:29 42.238°N 124.670°W 0.0
3.0 30km SW of Gold Beach, Oregon 2012-07-31 23:53:11 42.220°N 124.687°W 21.9
2.1 27km SW of Gold Beach, Oregon 2012-07-31 09:13:10 42.234°N 124.653°W 0.0
1.6 25km SW of Gold Beach, Oregon 2012-07-30 11:47:42 42.236°N 124.629°W 0.0
1.6 24km SW of Gold Beach, Oregon 2012-07-29 14:35:59 42.249°N 124.620°W 0.1
1.6 23km SW of Gold Beach, Oregon 2012-07-29 11:34:08 42.257°N 124.618°W 0.0
2.1 26km SW of Gold Beach, Oregon 2012-07-29 09:30:48 42.239°N 124.654°W 0.0

[dgavin]

This week three quakes so far, a 4.3 mag in the same location as the swarm two weeks ago. Plus a 4.5 and a 4.9 along the midplate-slip zone of the Jaun-de-Fuca rift area.

[dgavin]

Moderate Quake, plus two aftershocks on the 19th. A 5.5 Mag just off northern most washingtons coast. Followed by a 3.1 and then a 4.2 aftershook.

[dgavin]

Another aftershock this morning, 4.1 magnitude. All four events so far this week have been at 10km depth.

[dgavin]

Moving to a monthly report on this thread. 36 Jaun de Fuca/Cacadia Subduction Earthquakes this last month, three of them coming in at the 4.1 -4.5 magnitude range.

[Ara Pacis]

A question: I'm curious to know if any geologists have used strata along the shores or bathymetry to determine the angle of the NA plate in relation to the subducting plate to get an idea of how stressed it might be and how close it may be to snapping back.

[grapes]

A question: I'm curious to know if any geologists have used strata along the shores or bathymetry to determine the angle of the NA plate in relation to the subducting plate to get an idea of how stressed it might be and how close it may be to snapping back.

The earthquakes themselves can pretty much map that out, way deeper than bathymetry or strata, and more accurately--however not good enough to make any sort of stress calculations or timing predictions, which are mostly based on historical data, IIANACI.

[Ara Pacis]

The earthquakes themselves can pretty much map that out, way deeper than bathymetry or strata, and more accurately--however not good enough to make any sort of stress calculations or timing predictions, which are mostly based on historical data, IIANACI.

I'm not sure I follow, nor do I know what IIANACI means. I'm referring to bending stress. When the Japanese earthquake happened last year, parts of Sendai alongthe coast subsided and were inundated (before the tsunami hit), while the portion of plate near the subduction fault snapped upwards. So, it's like a portion of the crust did a seesaw motion along some pivot line. I was wondering if we have historical data that we can look at angle that the crust is deforming and how close that angle is to historical maxima which is relaxed via an earthquake.

[dgavin]

Ara,

Yes there has been investigation in the strata along the NW coast lines, indicating about a once per 700 year time frame for cosatal inudation due to subsidence after a likely megathrust EQ event.

This is what led to the seperate thread I made, about a major Oregon EQ actualy being predicted over the next few decades.

The native american legends about a mythical "Thunderbird", are now thought to be related to stories about these huge plate altering earthquake events. The times of these legends that are datable, seem to roughly coincide with the strata evidence of the megathrust events.

From the Strata evidence, there are some low lying area's along the coast that would likely be underwater after such an event. This may possibly include most of Pacific City and Beverly Beach state park, along with parts of Astoria, Lincoln City, Newport, Coos Bay, and Depot Bay.

[Ara Pacis]

Ara,

Yes there has been investigation in the strata along the NW coast lines, indicating about a once per 700 year time frame for cosatal inudation due to subsidence after a likely megathrust EQ event.

This is what led to the seperate thread I made, about a major Oregon EQ actualy being predicted over the next few decades.

The native american legends about a mythical "Thunderbird", are now thought to be related to stories about these huge plate altering earthquake events. The times of these legends that are datable, seem to roughly coincide with the strata evidence of the megathrust events.

From the Strata evidence, there are some low lying area's along the coast that would likely be underwater after such an event. This may possibly include most of Pacific City and Beverly Beach state park, along with parts of Astoria, Lincoln City, Newport, Coos Bay, and Depot Bay.

Right, but is that only related to periodicity or to an angular deviation from zero level?

[dgavin]

The strata evidence all seems to point to the periodicity of megathrust or larger quakes. Andd there seems to be some variences in how often.

The follow URL repost from another thread, I think will answer some of your questions about strata evidence and quakes.

http://www.pnsn.org/outreach/earthqu...biditeevidence

[Ara Pacis]

The strata evidence all seems to point to the periodicity of megathrust or larger quakes. Andd there seems to be some variences in how often.

The follow URL repost from another thread, I think will answer some of your questions about strata evidence and quakes.

http://www.pnsn.org/outreach/earthqu...biditeevidence

Nope. It doesn't even touch on tilt.

[dgavin]

Catching up here.

On October 28th a Large 7.8 Mag just north of the Juan De Fuca edge. Listing all events upto today.

M Location UTC Lat Lon D-km
4.1 165km SSW of Masset, Canada 2012-11-07 15:04:23 52.649°N 133.085°W 10.0
4.0 158km SSW of Masset, Canada 2012-11-06 15:47:13 52.717°N 133.062°W 10.0
4.6 194km SSE of Masset, Canada 2012-11-06 10:27:03 52.335°N 131.305°W 10.2
4.6 167km S of Masset, Canada 2012-11-04 18:27:19 52.522°N 132.346°W 20.3
4.9 186km S of Masset, Canada 2012-11-04 12:27:36 52.339°N 132.031°W 10.4
4.1 142km S of Masset, Canada 2012-11-04 07:42:15 52.741°N 131.859°W 10.0
4.0 156km S of Masset, Canada 2012-11-04 05:07:53 52.617°N 131.957°W 10.0
4.2 165km S of Masset, Canada 2012-11-03 17:49:14 52.535°N 132.007°W 22.4
4.0 187km SSW of Masset, Canada 2012-11-03 12:18:42 52.380°N 132.751°W 9.8
4.0 157km S of Masset, Canada 2012-11-03 09:48:24 52.611°N 132.378°W 10.1
4.4 166km S of Masset, Canada 2012-11-03 04:25:19 52.522°N 131.870°W 12.8
4.0 203km S of Masset, Canada 2012-11-02 08:37:10 52.186°N 132.160°W 10.4
4.5 182km S of Masset, Canada 2012-11-02 08:19:59 52.379°N 132.025°W 10.2
4.2 170km S of Masset, Canada 2012-11-02 07:15:45 52.497°N 131.759°W 11.0
4.9 161km S of Masset, Canada 2012-11-01 03:16:00 52.564°N 131.943°W 10.3
5.1 181km SSE of Masset, Canada 2012-11-01 03:15:23 52.500°N 131.100°W 1.0
4.0 165km S of Masset, Canada 2012-10-30 17:33:29 52.535°N 132.323°W 1.8
4.6 192km S of Masset, Canada 2012-10-30 14:10:59 52.285°N 131.948°W 10.0
4.7 208km S of Masset, Canada 2012-10-30 04:40:15 52.170°N 131.604°W 10.2
5.0 199km S of Masset, Canada 2012-10-30 02:55:08 52.222°N 132.116°W 19.2
6.2 210km S of Masset, Canada 2012-10-30 02:48:58 52.129°N 132.320°W 18.6
4.1 179km S of Masset, Canada 2012-10-30 00:35:09 52.423°N 131.655°W 10.0
4.0 166km S of Masset, Canada 2012-10-30 00:32:18 52.526°N 131.936°W 10.0
4.3 158km S of Masset, Canada 2012-10-29 22:00:33 52.593°N 132.273°W 10.0
4.6 188km SSE of Masset, Canada 2012-10-29 20:49:49 52.366°N 131.459°W 26.5
4.1 198km S of Masset, Canada 2012-10-29 16:33:08 52.231°N 131.971°W 10.0
4.0 216km S of Masset, Canada 2012-10-29 15:38:29 52.074°N 132.137°W 10.0
4.0 225km S of Masset, Canada 2012-10-29 15:15:02 51.989°N 132.225°W 10.0
4.0 224km S of Masset, Canada 2012-10-29 15:01:06 52.013°N 131.757°W 10.0
4.4 163km S of Masset, Canada 2012-10-29 12:05:14 52.574°N 132.552°W 10.2
4.1 119km S of Masset, Canada 2012-10-29 06:03:52 52.959°N 132.377°W 3.3
4.1 173km S of Masset, Canada 2012-10-29 03:47:55 52.461°N 132.190°W 10.0
4.0 182km S of Masset, Canada 2012-10-29 02:40:53 52.396°N 132.502°W 10.0
4.6 165km S of Masset, Canada 2012-10-29 01:49:02 52.530°N 131.965°W 10.0
4.3 184km S of Masset, Canada 2012-10-29 00:26:49 52.358°N 132.096°W 10.0
4.0 174km SSE of Masset, Canada 2012-10-29 00:18:50 52.612°N 130.948°W 10.0
4.1 126km SSE of Masset, Canada 2012-10-28 23:55:02 52.978°N 131.333°W 10.0
4.7 161km S of Masset, Canada 2012-10-28 23:34:23 52.570°N 132.291°W 10.0
4.9 144km S of Masset, Canada 2012-10-28 23:26:50 52.733°N 132.436°W 10.0
4.2 158km S of Masset, Canada 2012-10-28 23:11:17 52.608°N 132.454°W 12.5
4.7 189km S of Masset, Canada 2012-10-28 22:41:28 52.316°N 131.904°W 10.0
4.6 158km S of Masset, Canada 2012-10-28 21:38:19 52.602°N 131.893°W 24.7
5.1 166km S of Masset, Canada 2012-10-28 19:16:55 52.544°N 132.580°W 47.2
5.5 190km S of Masset, Canada 2012-10-28 19:09:56 52.315°N 131.860°W 14.8
5.4 151km SSW of Masset, Canada 2012-10-28 19:03:24 52.742°N 132.902°W 32.8
6.3 177km SSW of Masset, Canada 2012-10-28 18:54:16 52.480°N 132.793°W 20.0
4.3 169km SSE of Masset, Canada 2012-10-28 16:17:03 52.537°N 131.508°W 10.0
4.6 140km SSW of Masset, Canada 2012-10-28 15:59:11 52.786°N 132.595°W 10.0
4.4 161km SSW of Masset, Canada 2012-10-28 15:57:15 52.638°N 132.866°W 10.7
4.4 177km S of Masset, Canada 2012-10-28 15:48:45 52.427°N 132.261°W 10.0
4.4 191km S of Masset, Canada 2012-10-28 15:44:59 52.309°N 132.408°W 10.0
4.0 185km SSE of Masset, Canada 2012-10-28 15:42:21 52.404°N 131.422°W 10.0
4.3 135km S of Masset, Canada 2012-10-28 15:24:22 52.803°N 132.113°W 10.0
4.0 166km S of Masset, Canada 2012-10-28 15:10:34 52.516°N 132.066°W 10.0
4.4 178km S of Masset, Canada 2012-10-28 15:06:55 52.417°N 132.169°W 10.0
4.0 164km SSE of Masset, Canada 2012-10-28 14:14:28 52.588°N 131.440°W 7.7
4.2 154km S of Masset, Canada 2012-10-28 14:04:27 52.635°N 132.403°W 10.0
4.1 190km SW of Bella Bella Islands, Canada 2012-10-28 13:45:48 51.127°N 130.305°W 10.0
4.8 175km S of Masset, Canada 2012-10-28 13:09:14 52.445°N 131.842°W 10.0
4.1 127km S of Masset, Canada 2012-10-28 12:38:46 52.870°N 132.204°W 10.1
4.0 142km S of Masset, Canada 2012-10-28 12:18:00 52.750°N 131.769°W 10.0
4.1 161km S of Masset, Canada 2012-10-28 12:09:43 52.568°N 132.065°W 10.0
4.7 175km S of Masset, Canada 2012-10-28 11:53:21 52.438°N 132.201°W 10.5
4.8 180km S of Masset, Canada 2012-10-28 11:27:46 52.395°N 132.161°W 11.1
4.3 183km SSE of Masset, Canada 2012-10-28 11:17:22 52.400°N 131.566°W 10.6
4.0 172km S of Masset, Canada 2012-10-28 10:59:14 52.477°N 131.769°W 9.7
4.3 170km S of Masset, Canada 2012-10-28 10:50:32 52.484°N 131.945°W 10.3
4.7 157km S of Masset, Canada 2012-10-28 10:45:50 52.621°N 132.500°W 10.2
4.5 145km SSW of Masset, Canada 2012-10-28 10:23:09 52.753°N 132.678°W 10.2
4.3 171km S of Masset, Canada 2012-10-28 10:10:27 52.482°N 132.247°W 10.3
4.3 119km S of Masset, Canada 2012-10-28 10:04:37 52.948°N 132.285°W 10.0
4.1 127km S of Masset, Canada 2012-10-28 09:52:58 52.892°N 131.733°W 10.0
4.4 127km S of Masset, Canada 2012-10-28 09:45:39 52.886°N 132.392°W 10.2
4.4 221km S of Masset, Canada 2012-10-28 09:41:16 52.029°N 132.187°W 10.0
4.6 196km S of Masset, Canada 2012-10-28 09:36:36 52.258°N 132.343°W 10.3
4.4 173km SSE of Masset, Canada 2012-10-28 09:22:50 52.551°N 131.193°W 10.0
5.1 197km S of Masset, Canada 2012-10-28 09:17:27 52.243°N 131.996°W 10.0
4.2 215km S of Masset, Canada 2012-10-28 09:15:48 52.102°N 131.653°W 10.0
4.2 277km SSW of Masset, Canada 2012-10-28 08:47:38 51.634°N 133.314°W 10.0
4.3 216km S of Masset, Canada 2012-10-28 08:22:04 52.067°N 132.073°W 10.0
5.0 198km SSE of Masset, Canada 2012-10-28 07:25:22 52.270°N 131.493°W 10.6
4.9 140km S of Masset, Canada 2012-10-28 07:16:37 52.775°N 132.456°W 11.4
4.6 212km S of Masset, Canada 2012-10-28 07:12:14 52.109°N 132.221°W 10.0
4.4 231km S of Masset, Canada 2012-10-28 07:02:19 51.941°N 131.836°W 10.8
5.0 203km SSE of Masset, Canada 2012-10-28 06:16:53 52.268°N 131.212°W 11.5
4.5 139km SSW of Masset, Canada 2012-10-28 05:51:17 52.815°N 132.714°W 10.3
4.3 181km SSE of Masset, Canada 2012-10-28 05:47:08 52.430°N 131.451°W 10.1
4.1 248km S of Masset, Canada 2012-10-28 05:38:38 51.786°N 132.312°W 10.1
4.3 211km S of Masset, Canada 2012-10-28 05:21:36 52.140°N 131.571°W 10.0
4.3 169km S of Masset, Canada 2012-10-28 05:15:12 52.499°N 132.222°W 10.1
4.5 178km S of Masset, Canada 2012-10-28 05:02:49 52.409°N 132.165°W 10.3
4.3 180km S of Masset, Canada 2012-10-28 04:54:46 52.403°N 132.439°W 10.1
4.7 155km SSW of Masset, Canada 2012-10-28 04:41:05 52.648°N 132.597°W 20.0
4.6 140km SSW of Masset, Canada 2012-10-28 04:33:51 52.906°N 133.120°W 10.0
5.1 254km SSW of Masset, Canada 2012-10-28 04:25:17 51.930°N 133.642°W 20.0
4.8 183km S of Masset, Canada 2012-10-28 03:52:25 52.372°N 131.823°W 20.0
5.8 154km S of Masset, Canada 2012-10-28 03:14:10 52.629°N 132.243°W 10.0
7.8 141km S of Masset, Canada 2012-10-28 03:04:09 52.742°N 132.131°W 20.1