By:Hamizah Hanim

Hamzah,Helen Ellwood,

andZoltán Erdős

Contents• Obtaining measurements

• Processing data

• Results

• Interpretation

Study Area

Line B

(4.5km)

Line A

(1km)

Line C

(4.2km)

N

Measuring Gravity

The Lacoste-Romberg Gravity Meter

Measuring Elevations

Geodimeter

Processing Method

Corrections needed for:

1. Tides

2. Instrument drift

Due to elastic creep in springs

3. Differences in latitude

g increases towards poles

Processing Method

4. Height of measurement above reference datum:

Free-Air Correction = +0.308 mGal/m

5. Extra mass between measurement and reference datum:

Bouguer Correction = -0.4185ρhWhere ρ=density (gm/cm3) and h = height above datum (m)

6. Effect of surrounding terrain

NNW SSE

ρ = 2 gm/cm3

SW NE

ρ = 2 gm/cm3

SW NE

ρ = 2 gm/cm3

Buoguer Anomaly Map with stations colour-coded according to measured anomaly

Comparison With Resistivity Results

Line C anomaly has been filtered to remove long and very short wavelength variations, and compared with resistivity inversion result.

A Possible Model for Line B

Basement, ρ=2.67g/cm3

A Possible Model for Line C

Another Possibility for Line C

Gravity interpretation is non-unique

Geological and Topographic Map of Region

Summary• 3 lines: A – Oreg-Hegy, B&C – traversing Enying

Ridge;• Various corrections needed to produce relative

Bouguer Anomaly map;• Anomaly profiles each represent complex

structures on many different scales;• There is no evidence for a tectonic origin for the

Enying Ridge formation.• Acknowledgements: Res1 and Res2 for their

results; Greg Houseman and Piroska Lorinczi for all their help.

Question Time

Measuring gravity gets lonely