| Title | Tectonic Deformation of a Lacustrine Mudstone at Soda Lake Geothermal Field, Western Nevada, Usa, from 3D Seismic Interpretation |
|---|---|
| Authors | T. Kent and J. N. Louie |
| Year | 2013 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | 3D Seismic, Tectonics, Geothermal, Walker Lane |
| Abstract | The transition between the two structural and fault regimes of the right-lateral Walker Lane and the extensional Basin and Range, Nevada, allows for complex transtensional fault interactions. This study investigates this tectonic shift in the Carson Sink using the fault offsets of a paleo-planar lacustrine mudstone in a 3D seismic-reflection data volume at the Soda Lake Geothermal Field. The 3D and threecomponent reflection seismic survey covers an area of 34 sq km with 8374 source points and 3001 receivers. A Recent sandstone/mudstone package is a strong and the most expansive reflector in this survey, appearing from 0.2 to 0.3 seconds, at an approximate depth of 240 m. The interpreted mudstone reflectors illuminate a fault map of recent active tectonics in this basin. Fault offsets of this unit demonstrate post-depositional structural deformation of the Soda Lake geothermal field. Using OpendTect® allowed multiple steps in specialized workflows to facilitate the interpretation of faults and horizons in this seismic-reflection data volume. A dip-steered, median-filtered, and diffusion-filtered volume gave sharper contrasts at the faults. Using this faultenhanced data volume assisted the interpretation of the surface of the mudstone horizon and the faults that offset reflectors above and below the unit. The fault patterns show en echelon fault steps, large left bends and some antitheticstriking faults. Total horizontal offset across all the faults is 96 m across 5.4 km, yielding 1.8% as a value for recent extensional strain across the survey. The horizon map of the mudstone has a relative low point in the accommodation zone that accompanies a left bending fault and coincides with the most productive part of the geothermal field. A structural ramp between the major faults on the west side suggests a structural interpretation as a normal-fault stepover zone, supposing a lack of strike-slip motion or pullapart mechanics. |