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TRAINING ON SURFACE EXPLORATION STUDIES FOR GEOTHERMAL RESOURCES AND

DEVELOPMENT OF CONCEPTUAL MODELS

UNDER THE AUSPICES OF INTERIM PROJECT COORDINATION UNIT OF THE AFRICA

GEOTHERMAL CENTER OF EXCELLENCE

7—12 April, Asmara, Eritrea

Gravity – regional residual separation

Kristján Ágústsson, Iceland GeoSurvey

Slides from Gylfi Páll Hersir

Regional field – regional and residual anomalies

Bouguer anomaly fields are often characterized by a broad,

gently varying, regional anomaly on which superimposed

higher wave number local anomaly occurs. Usually in gravity

surveying it is the local anomalies that are the prime interest

and the first step is to remove the regional field.

ICELAND GEOSURVEY

Gravity measurements in an area show an anomaly, which is over lay a long wavelength anomaly. To extract the true shape of the short wave anomaly the regional field must be separated out and removed.

ICELAND GEOSURVEY

In this case the regional field is straight forward as it strikes NW-SE with a dip towards the SW.

ICELAND GEOSURVEY

The residual map shows a circular 6 mGalnegative anomaly.

ICELAND GEOSURVEY

ICELAND GEOSURVEY

Depth of source

Halfwitdth ~ (1500-750)/2 ~ 750 m

Depth = 1.3* halfwdth = 480 m

What needs to be done further?