Publication Date:
2016-05-23
Description:
We present the first results of an electromagnetic survey for gas hydrates offshore Taiwan using a novel marine controlled-source electromagnetic system. Seismic evidence suggests the presence of gas hydrates and free gas in both accretionary (Four-Way-Closure) and erosional (Formose Ridge) settings to the southwest of the island, but complementary geophysical techniques are required to further quantify the distribution and concentration of the deposits. Electromagnetic experiments were conducted along profiles in both regions and show an increase in apparent resistivity at depth, which may be associated with the presence of methane hydrates. However, both profiles are characterized by severe bathymetric relief, in some cases having slope angles greater than 30 degrees, such that the apparent resistivity section may be biased by tilts of the instruments. We therefore derive a first-order bathymetric correction which can be applied to apparent resistivities and tested the correction procedure on data collected at Four-Way-Closure. Results show that increased apparent resistivities persist and reach up to 7Ωm, which suggests the presence of significant concentrations of hydrate or free gas at this location.
Type:
Article
,
NonPeerReviewed
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