Results from strainmeter recordings of cascadia ets events
Download
1 / 15

Results from Strainmeter Recordings of Cascadia “ETS” events - PowerPoint PPT Presentation


  • 169 Views
  • Uploaded on

Results from Strainmeter Recordings of Cascadia “ETS” events. Work by Evelyn Roeloffs, Wendy McCausland, and Paul Silver 2 March 2009. Areal strain data from many PBO borehole strainmeters in Cascadia are of poor quality

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Results from Strainmeter Recordings of Cascadia “ETS” events' - absolom


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Results from strainmeter recordings of cascadia ets events l.jpg

Results from Strainmeter Recordings of Cascadia “ETS” events

Work by Evelyn Roeloffs, Wendy McCausland, and Paul Silver

2 March 2009

Cascadia 2007 and Beyond Workshop, Seattle


Horizontal strain components derived from strainmeter data l.jpg

Areal strain data from many PBO borehole strainmeters in Cascadia are of poor quality

Shear strain (Differential extension and engineering shear) coupling is generally good

For strainmeters that could be tidally calibrated, the tidal calibrations yield shear strains that are 3 to 1.5 times larger than the PBO calibration coefficients

Recent work by Duncan Agnew indicates shear strain tides are not well modeled

More work needed on removing surface-loading effects and detrending

Horizontal Strain Components derived from Strainmeter Data

Cascadia 2007 and Beyond Workshop, Seattle


Cascadia aseismic slip events l.jpg
Cascadia Aseismic Slip Events Cascadia are of poor quality

Cascadia 2007 and Beyond Workshop, Seattle


Pbo borehole strainmeters in cascadia l.jpg
PBO Borehole Strainmeters in Cascadia Cascadia are of poor quality

Cascadia 2007 and Beyond Workshop, Seattle


What do we expect l.jpg
What do we expect? Cascadia are of poor quality

  • Simple Model: 1cm slip, 10km-wide fault centered on 40 km depth contour.

  • Example: B004 for 2007 event.

Northward Rupture

Southward Rupture

Cascadia 2007 and Beyond Workshop, Seattle


Slide6 l.jpg

2007 Tremor and Slow Slip Event Cascadia are of poor quality

Tremor locations

within 50-60 km

of strainmeter

coincide with

onset of strain

signals

North

N

N

Tremor locations from A Wech

of Univ. of Washington and

H. Kao of Geol. Survey of

Canada

South

Cascadia 2007 and Beyond Workshop, Seattle

N


2008 tremor and slow slip event l.jpg
2008 Tremor and Slow Slip Event Cascadia are of poor quality

Tremor

locations

within

50-60 km of

strainmeter

coincide

with onset

of strain

signals

North

Bilateral

migration

Tremor locations from

A Wech of Univ. of

Washington and

H. Kao of Geol.

Survey of Canada

South

Cascadia 2007 and Beyond Workshop, Seattle


Slide8 l.jpg

Which comes first, the tremor or the slow slip? Cascadia are of poor quality

For all the data, the onsets are simultaneous to within a few hours.

At B018, based on 30-minute strainmeter data and 30-minute tremor counts the onsets of the tremor and slow slip are simultaneous.

Cascadia 2007 and Beyond Workshop, Seattle


Close up of b012 l.jpg
Close-up of B012 Cascadia are of poor quality

Tremor locations from

H. Kao of Geol. Survey of

Canada

Cascadia 2007 and Beyond Workshop, Seattle


Slide10 l.jpg

Simultaneous Onset within 1/2 hour Cascadia are of poor quality

Tremor locations from

A. Wech of Univ.

of Washington

Cascadia 2007 and Beyond Workshop, Seattle


Slip does accompany inter ets tremor bursts l.jpg
Slip does accompany inter-ETS tremor bursts Cascadia are of poor quality

  • - For 2 of the largest 3 inter-ETS events, there is discernible strain consistent with known tremor and slow slip events.

  • Possible exception for June 2007 tremor

  • Results indicate that even when there is tremor comparable to that observed during recurrent ETS events, the strain is much (1/6th as much) smaller than during the recurrent ETS events.

  • Exception at B012 for October 2007

Cascadia 2007 and Beyond Workshop, Seattle


Slow slip event recorded by strainmeter little or no gps signal l.jpg
Slow slip event recorded by strainmeter, little or no GPS signal

2006

2006

K. Wang et al., GRL, 2008

Cascadia 2007 and Beyond Workshop, Seattle


Question 2 inter event tremor activity 4 candidate events l.jpg
Question 2: Inter-Event Tremor Activity- 4 Candidate Events signal

June 2007

No discernible

strain

Washington

Located Tremor Counts

March 2008

Discernible

strain

Vancouver Island

Located Tremor Counts

October 2007

Discernible

strain

Tremor locations from

A Wech of Univ. of

Washington and

H. Kao of Geol.

Survey of Canada

Cascadia 2007 and Beyond Workshop, Seattle

Days after 1/1/2007


October 2007 inter event tremor bursts l.jpg
October 2007 signalInter-Event TremorBursts

Southward

propagation

past B012

Tremor locations from

H. Kao of Geol. Survey of

Canada

Northward

propagation

stopping near

B007

Cascadia 2007 and Beyond Workshop, Seattle

Tremor locations from

A. Wech of Univ. of

Washington


March 2008 b018 l.jpg
March 2008 B018 signal

B018 March 2008 blowup

- Tremor and strain have indistinguishable onsets (< 30 min)

- Southward propagating rupture

- Located at least 10 km updip from B018

Cascadia 2007 and Beyond Workshop, Seattle


ad