11 William Frank - MIT ERL William Frank.pdf · Slide5& 2016&Annual&Founding&Members&Meeting...

Pinpointing transient aseismic slip at depth with seismological observations

William FrankNSF Postdoctoral Fellow,

Department of Earth, Atmospheric, and Planetary Sciences

In collaboration with N. Shapiro, G. Prieto, M. Campillo, A. Husker, V. Kostoglodov, A. Gusev, M. Radiguet, B. Rousset, and N. Cotte

MIT Earth Resources Laboratory 2016 Annual Founding Members Meeting

May 18th, 2016

2016 Annual Founding Members Meeting

How is tectonic stress accommodated?

Seismic Cycle

‣ Updip: earthquakes (brittle)

‣ Downdip: aseismic sliding (ductile)

Modified from Gomberg, GSAB, 2010


How is tectonic stress accommodated?

Seismic Cycle

‣ Updip: earthquakes (brittle)

‣ Downdip: aseismic sliding (ductile)

What happens in between in the frictional transition zone?


Transition zone


What do we know about the transition zone?

‣ High pore fluid pressure → low effective stress

‣ Industrial context: Parallels with microseismicity?

‣ Partitioning of deformation between seismic and aseismic

‣ Industrial context: How does (a)seismic slip in HF regions occur? Can we track it?


Transition zone


Seismic vs. aseismic deformation in the transition zone

Seismic Aseismic

Name (jargon) Low-‐frequency earthquake Slow slip event

Duration Seconds Days to years

Recurrence time Seconds Weeks to years

Rupture length ~100 meters (?) >100 kilometers

Slip Microns (?) Centimeters

Moment magnitude -‐1 to 1 5.5 to 7.5

Instrument Seismometer GPS/tiltmeter/strainmeter


Repeating seismicity in the transition zone

Transition zone


4 hours


Transition zone


4 hours

Repeating seismicity in the transition zone


Example waveforms for repeating seismic event

PLAT HHNXALI HHNTONA HHNSATA HHNZACA HHN

Norm

alize

d G

roun

d Ve

locit

y

TOMA HHNCIEN HHNBUCU HHNCASA HHN

7050 7055 7060 7065 7070 7075 7080 7085AMAC HHN

Time (s)

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


Detecting other events from the same seismic source

PLAT HHNXALI HHNTONA HHNSATA HHNZACA HHN

Norm

alize

d G

roun

d Ve

locit

y

TOMA HHNCIEN HHNBUCU HHNCASA HHN

7050 7055 7060 7065 7070 7075 7080 7085AMAC HHN

Time (s)

Waveform matching search:

‣ Template event consists of:

‣ Network waveforms

‣ Network moveout


Events detected with waveform matching: different events, same source

Visualizing cataloged seismicity


Visualizing cataloged seismicity

Events detected with waveform matching: different events, same source


Repeating earthquakes in the Mexican subduction zone

Modified from Frank et al., JGR, 2014

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


What does a GPS “see” on the surface?


Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


Aseismic slip accompanied by episodic seismicity


Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t

Loading

Release

Jan ‘05 Jan ‘06 Jan ‘07


Aseismic signature of a Mw 7.5 slow slip event

Loading

Release

Jan ‘05 Jan ‘06 Jan ‘07Modified from Kostoglodov et al., GRL, 2010

Does slow slip occur at other times?

‣ Not obvious on GPS position time series…


Characteristic episodic seismicity during slow slip?


Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


When else does seismicity stretch across source region?


Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t



Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

tWhen else does seismicity stretch across source region?


Aligning GPS data on seismicity episodes

Modified from Frank et al., GRL, 2015

−150 −100 −50 0 50 100 150−5

−4

−3

−2

−1

0

1

2

3

4

5

Days relative to episode

Surfa

ce d

ispl

acem

ent (

mm

)

MEZC

IGUA

Rele

ase →

Loading →

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


Aligning GPS data on seismicity episodes


−150 −100 −50 0 50 100 150−5

−4

−3

−2

−1

0

1

2

3

4

5


Surfa

ce d

ispl

acem

ent (

mm

)

MEZC

IGUA

x7

Rele

ase →

Loading →

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


Average GPS signal during seismicity episodes


−150 −100 −50 0 50 100 150−5

−4

−3

−2

−1

0

1

2

3

4

5


Surfa

ce d

ispl

acem

ent (

mm

)

MEZC

IGUA

x7

Rele

ase →

Loading →

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t


Hidden slow slip pulled out of the noise

Modified from Frank et al., GRL, 2015 −120 −60 0 60 120−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Su

rfa

ce

dis

pla

ce

me

nt

(mm

)

AC

YA

CO

YU

DO

AR

ME

ZC

IGU

AY

AIG

So

uth

No

rth

−150 −100 −50 0 50 100 150−5

−4

−3

−2

−1

0

1

2

3

4

5


Surfa

ce d

ispl

acem

ent (

mm

)

MEZC

IGUA

Rele

ase →

Loading →

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t

Lowered geodetic noise level with seismicity catalog


Take away messages

Modified from Frank et al., GRL, 2015 −120 −60 0 60 120−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Su

rfa

ce

dis

pla

ce

me

nt

(mm

)

AC

YA

CO

YU

DO

AR

ME

ZC

IGU

AY

AIG

So

uth

No

rth

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus

t‣Seismicity accompanies (hidden) aseismic slip



Take away messages

−120 −60 0 60 120−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Su

rfa

ce

dis

pla

ce

me

nt

(mm

)

AC

YA

CO

YU

DO

AR

ME

ZC

IGU

AY

AIG

So

uth

No

rth

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus


‣Precise seismicity characterization can provide new observations

‣Tiltmeter/strainmeter in shallow environments?



Take away messages

−120 −60 0 60 120−1.0

−0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Su

rfa

ce

dis

pla

ce

me

nt

(mm

)

AC

YA

CO

YU

DO

AR

ME

ZC

IGU

AY

AIG

So

uth

No

rth

Oce

anic

slab

Slow

slip

Repe

atin

gse

ismic

ity

Cont

inen

tal

crus


‣Precise seismicity characterization can provide new observations

‣Tiltmeter/strainmeter in shallow environments?

Interdisciplinary datasets essential to observe the full spectrum of

faulting and deformation

11 William Frank - MIT ERL William Frank.pdf · Slide5& 2016&Annual&Founding&Members&Meeting...

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