Seismic Imaging of Seneca and Cayuga Lakes Christopher

Seismic Imaging of Seneca and Cayuga Lakes: Christopher A. Scholz Syracuse University cascholz@syr. edu http: //rifts. syr. edu

Collaborators: New York State Museum Financial support from New York State Energy Research Development Authority In-kind processing support from Sterling Seismic Services, Ltd.

Cruise participants: Hobart-William Smith Colleges John Nichols John Abbott John Halfman Syracuse Univ. Chris Scholz Mike Mc. Glue Peter Cattaneo Kiram Lezzar Nick Peters New York State Museum Bob Lyons RJ Hartwell Rich Nyahay Justin Deming Phil Arnold Courtney Lugert Rose Schulze Brian Slater

Earth Satellite Corp. , 1997, Remote Sensing and Fracture Analysis for Petroleum Exploration of Ordovician to Devonian Fracture Reservoirs of New York

Outline • Small Lake Seismics: Acquisition issues and parameters: Practical experiences from the Finger Lakes • Data processing efforts • Preliminary interpretations and key geologic features • The October ’ 02 Survey – what worked and what didn’t

Acquisition Parameters • • • Approach: Simpler is better!!! 24 -bit recording 12 -fold data 12. 5 m groups; ~625 m total offset 5 m streamer depth; 2 m gun depth Differential GPS acquisition (sub-meter accuracy) • Streamer leveling: Digicourse Birds

Acquisition Equipment • OYO DAS-1 48 -channel, Digital Seismic Acquisition System • ELICS Delph 2 high-resolution seismic acquisition system (for real-time QC) • 2 x 40 c. i. I-O Sleeve Gun airgun array • Portable diesel-powered seismic air compressors (58 SCFM total) • Single channel streamer (for real-time QC) • 48 Ch. 600 m (active) ITI Stealth array seismic streamer w/ 150 m lead-in (Primary Streamer)

Acquisition Challenges • • • Small vessel Short (but solid!) streamer Crooked line navigation Limited compressor capability…. Streamer levelers marginal at slow shooting speeds • Limited daylight • Recreational boaters • Environmentally sensitive setting

Hobart William Smith Colleges R/V William Scandling, Seneca Lake

I-O Sleeve Gun Array (2 X 40 c. i. guns)

I-O Sleeve Gun Array (2 X 40 c. i. guns)

I-O Sleeve Gun Array (2 X 40 c. i. guns)

The October ‘ 02 Survey ~95 km total acquisition: Cayuga, Seneca – two axial lines each

Data Processing • Initial processing by SU, subsequent intensive processing by Sterling Seismic Services, Ltd. • Significant changes between Brute stack Enhanced stack Kirckhoff Migration + FK-filtering

Data Processing • • Crooked line geometry High-resolution radon demultiple routine Kirckoff migration FK filter

Brute stack

Enhanced stack

Kirckhoff Migration

Kirckhoff Migration + F-K Filter

Lineaments Inferred Fault Tracklines Faults

Enhanced stack – full line

Initial Observations • Up to 200 m of Quaternary fill • Bedrock surface follows regional dip • Rugged bedrock topography – tracklines not uniformly on top of bedrock thalweg • Considerable relief on high-amplitude events below Quaternary fill !? ! • Offsets on Paleozoic reflections – 20 ms or more

Enhanced stack – full line

Exposed bedrock Apparent Offsets

Survey Challenges – Post-mortem • Seismic source constraints – not a limiting factor • High velocity section – perhaps the major issue; longer streamer preferable • Thick Quaternary fill and narrow bedrock valley – side echo effects not a major problem, but complex bedrock surface morphology had major impact • Limited budget and cruise window – processing budget; cruise window limiting factor = amount of daylight available • Limited number of nearby wells, with full log suites