water tectonics and the roots of utah's earthquakes

Water Tectonics andthe Roots of Utah’s

Earthquakes

Tony Lowry

Weather Forecasting:

TemperaturePressure

Water

Flow of Energy

& Matter

Seismic Forecasting?

Seismic Forecasting?

Seismic Forecasting?

Mw 6.9 Borah Peak earthquake

? ? ?

Seismic Forecasting?

Inte

rmou

ntai

nS

eism

ic B

elt

Crust(Feldspar,Quartz)

Mantle(Olivine,Pyroxene)

Cold (~0°C)

Hot (~1350°C)

Brittle Stre

ngth

Crustal Flow Strength

Mantle Flow Strength

Earthquakes here!

Active TA Seismic

Past TA Seismic

Permanent Seismic

Permanent GPS

Electrical (MT)

EarthScope

Higher H2O

Property Higher Temp.

Seismic Velocity

Electrical

Conductivity

MassDensity

Flow

Strength

Partial Melt

Hot?Wet?

Slow

High

Cold?Dry?

Fast

Low

!

!

These arethe oneswe need formodeling.

From Becker, Lowry, et al., Nature, 2015

Earthquake Distribution Gravitational Potential Energy Crustal Thickness

Lithosphere Strength Seismic Lithosphere Depth Dynamic Topography

Becker, Lowry, et al., Nature, 2015

Wait… Dynamic topography? What is that?

Dynamic Topography

Schmandt & Lin, GRL, 2014 Becker, Lowry, et al., Nature, 2015

Then serendipity strikes…

Bec

ker,

Low

ry, e

t al.,

Nat

ure,

201

5

Random at

95 %confidence

Bec

ker,

Low

ry, e

t al.,

Nat

ure,

201

5

Bec

ker,

Low

ry, e

t al.,

Nat

ure,

201

5

And what does it mean for earthquakes?Our model neglected the lithosphere:

But in reality “dynamic elevation rate” is better thought of as a“lithospheric loading rate”

that adds to membrane stress and stretching of thelithosphere.

High viscosity fluid

Low viscosity fluid

Visco-elasto-plastic lithosphere

“Uplift”

So where does water come into this?

“Dry” mantle peridotite “Hydrous” mantle serpentinite

How would water get there?

Kanda et al., in prep, 2015

Wannamaker et al., Nature, 2009

Schmandt & Lin, GRL, 2014

Higher H2O

Property Higher Temp.

Seismic Velocity

Electrical

Conductivity

MassDensity

Flow

Strength

Partial Melt

Te and StrengthBritt

le Stre

ngth

Flow

Crust

Mantle

zn

f

YSE

Elastic

Inviscid

zn

f

Flow Strength…

depends on:• Temperature• Rock Type (pyroxene > olivine > feldspar > quartz)

• Water Content.

Crust

Mantle

Flow Strength…

depends mostly on:

• Rock Type (crust thickness)• Temperature

• Water Content

Flow Strength…

depends mostly on:

• Rock Type (Qtz or Fsp?)• Temperature

• Water Content

Flow Strength…

depends mostly on:

• Rock Type

• Temperature

• Water Content

Flow Strength…

depends mostly on:

• Rock Type

• Temperature

• Water Content

Wet (saturated) end-member Dry end-member

Bec

ker,

Low

ry, e

t al.,

Nat

ure,

201

5

Thank You

Inte

rmou

ntai

n S

eism

ic B

elt

Electrical Conductivity Seismic Velocity

Electrical conductivity structure is dominantly water variation below ~200 km depth…

But difficult to interpret at shallower depths, even when coupled with seismic imaging

Schmandt & Lin, GRL, 2014

Meq

bel e

t al.,

EP

SL,

201

4