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Inferring shear-velocity structure of the upper 200 m using cultural ambient noise at the Ngatamariki geothermal field, central North Island, New Zealand

Francesco Civilini, Aasha Pancha, Martha Kane Savage, Steven Sewell and John Townend
Inferring shear-velocity structure of the upper 200 m using cultural ambient noise at the Ngatamariki geothermal field, central North Island, New Zealand
Interpretation (Tulsa) (August 2016) 4 (3): SJ87-SJ101

Abstract

We have determined subsurface structure using the refraction microtremor (ReMi) method at the Ngatamariki geothermal field, Central North Island, New Zealand. The local geology is such that refraction and reflection studies are hindered by energy scattering and attenuation in the near-surface layers. The ReMi method uses surface waves from ambient noise and active sources to determine S-wave velocities in the shallow subsurface. We have deployed two lines of 72-channel, 10 Hz vertical geophones with 10 m spacing, and we were able to model near-surface S-wave velocity to depths of 57-93 m for 2D profiles and as much as 165 m for 1D profiles. Shear-velocity anomalies were detected on one line that were spatially correlated with a fault. The location of the fault was previously inferred from stratigraphic offset in the geothermal wells, suggesting that the ReMi method can provide important constraints on near-surface geology in noisy geothermal settings.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 4
Serial Issue: 3
Title: Inferring shear-velocity structure of the upper 200 m using cultural ambient noise at the Ngatamariki geothermal field, central North Island, New Zealand
Affiliation: Victoria University of Wellington, Wellington, New Zealand
Pages: SJ87-SJ101
Published: 201608
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 54
Accession Number: 2017-002791
Categories: Economic geology, geology of energy sourcesApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, sketch maps
S38°40'00" - S38°30'00", E176°04'60" - E176°15'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201703
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