Geology 492/692 Field Geology 492/692 Field ProjectProject

Hoping to put Fernley and Hazen on the Hoping to put Fernley and Hazen on the Fault MapFault Map

ReMi DataReMi Data

ReRefraction fraction MiMicrotremor (ReMi) Methodcrotremor (ReMi) Method

• Developed to provide quick an easy site specific shaking hazard assessment.

• Uses microtremor noise as source.• Rayleigh-wave phase-velocity dispersion curves are

picked to determine the slowest surface wave velocities at any given frequency.

• Forward modeled to produce a shear-velocity-depth sounding.

• Can estimate shear velocity with 20% accuracy to depths of up to 100m.

• Average V30 can be estimated.

Using ReMi to Find Faults?Using ReMi to Find Faults?

• Theoretically possible if fault offset displaces units with observably different shear wave velocities.

• Might be able to detect rubble zones or flower structures.

• Likely not a marketable method for fault hunting.

This StudyThis Study

• Characterized V30 at 20 sites.

– 8 Northern Fernley Hills– 12 Hazen Flat

• Fernley studies conducted with 24 channel, 10 m spacing, Bison line.

• Hazen Studies conducted with a 20 Texan, 10 m spacing array.

LocationLocation

Results (Fernley)Results (Fernley)V30 vs. Northing (Fernley: West access road)

0

100

200

300

400

500

600

700

800

4380500 4381000 4381500 4382000 4382500 4383000

Northing (m)

V3

0 (

m/s

)

V30 vs Northing (Fernley: East access road)

0

100

200

300

400

500

600

700

4380600 4380650 4380700 4380750 4380800 4380850 4380900

Northing (m)

V3

0 (

m/s

)

Results (Hazen)Results (Hazen)

V30 vs Easting (Hazen: West of canal)

0

100

200

300

400

500

600

700

800

323300 323400 323500 323600 323700 323800

Easting (m)

V3

0 (

m/s

)

V30 vs. Northing (Hazen: North section of main access road)

0

100

200

300

400

500

600

700

4377000 4377500 4378000 4378500 4379000

Northing (m)

V3

0 (

m/s

)

Data Comparison (Fernley West)Data Comparison (Fernley West)Magnetics and ReMi vs. Northing (Fernley)

50900

51000

51100

51200

51300

51400

51500

4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (m)

Ma

gn

eti

sm

(n

T)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

Magnetics

ReMi

Gravity vs. ReMi (Fernley)

2548.6

2548.8

2549

2549.2

2549.4

2549.6

2549.8

2550

2550.2

2550.4

2550.6

4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (UTM)

Bo

ug

ue

r A

no

ma

ly (

mG

al)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

Gravity

ReMi

EM and ReMi Data vs. Northing

0

50

100

150

200

250

300

4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (m)

Ap

pa

ren

t R

es

isti

vit

y (

Oh

m m

)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

EM

ReMi

Data Comparison (Fernley East)Data Comparison (Fernley East)Magnetics and ReMi vs. Northing

51700

51800

51900

52000

52100

52200

52300

52400

52500

4379500 4380000 4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (m)

Ma

gn

eti

sm

(n

T)

0

100

200

300

400

500

600

700

v3

0 (

m/s

)

Magnetics

ReMi

EM and ReMi vs. Northing (Line 2)

0

50

100

150

200

250

4380000 4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (m)

Ap

pa

ren

t R

es

isti

vit

y (

Oh

m m

)

0

100

200

300

400

500

600

700

V3

0 (

m/s

)

EM

ReMi

Gravity vs. ReMi (Fernley East)

2549

2549.5

2550

2550.5

2551

2551.5

2552

2552.5

4379500 4380000 4380500 4381000 4381500 4382000 4382500 4383000 4383500

Northing (UTM)

Bo

ug

uer

An

om

aly

(mG

al)

0

100

200

300

400

500

600

700

V30

(m

/s)

Gravity

ReMi

Data Comparison (Hazen South)Data Comparison (Hazen South)

Gravity vs. ReMi (Hazen South)

2558.4

2558.5

2558.6

2558.7

2558.8

2558.9

2559

2559.1

2559.2

2559.3

323300 323400 323500 323600 323700 323800 323900 324000

Easting UTM (m)

Sim

ple

Bo

ug

ue

r A

no

mo

ly (

mG

al)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

Gravity

ReMi

EM vs ReMi (Hazen South)

0

50

100

150

200

250

300

350

323300 323400 323500 323600 323700 323800 323900

Easting (m)

Ap

pa

ren

t R

es

isti

vit

y (

Oh

m-m

)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

EM

ReMi

Magnetics vs ReMi (Hazen South)

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

1800.0

2000.0

323200 323300 323400 323500 323600 323700 323800 323900 324000 324100

Easting (m)

Ma

gn

eti

sm

(n

T)

0

100

200

300

400

500

600

700

800

V3

0 (

m/s

)

Magnetics

ReMi

Data Comparison (Hazen North)Data Comparison (Hazen North)

Gravity vs. ReMi (Hazen North)

2555

2555.5

2556

2556.5

2557

2557.5

2558

2558.5

2559

2559.5

2560

4376500 4377000 4377500 4378000 4378500 4379000 4379500

Northing (m)

Sim

ple

Bo

ug

ue

r A

no

mo

ly (

mG

al)

0

100

200

300

400

500

600

700V

30

(m

/s)

Gravity

ReMi

Magnetics vs ReMi (Hazen North)

0.0

500.0

1000.0

1500.0

2000.0

2500.0

4377000 4377200 4377400 4377600 4377800 4378000 4378200 4378400 4378600 4378800 4379000 4379200

Northing (m)

Ma

gn

eti

sm

(n

T)

0

100

200

300

400

500

600

700

V3

0 (

m/s

)

Magnetics

ReMi

EM vs. ReMi

0

50

100

150

200

250

300

350

4377000 4377500 4378000 4378500 4379000 4379500

Northing (m)

Ap

pa

rre

nt

Re

sis

tiv

ity

(O

hm

-m)

0

100

200

300

400

500

600

700

V3

0 (

m/s

)

Magnetics

ReMi

ConclusionsConclusions

• ReMi “anomalies” do align themselves with observed anomalies from other techniques about 75% of the time.

• However, ReMi did not confidently determine the location of any structures.

• Best as a corroborative technique for fault hunting.