1. Preliminary Results, Helicopter Electromagnetic and Magnetic Survey of the Seco Creek Area, Medina and Uvalde Counties, Texas Bruce D Smith, Richard Irvine, Charles D. Blome, Allan Clark, and David V Smith

2. Index map

3. Geologic studies

4. Preliminary geologic map from Kyle and Collins HEM SURVEY RECHARGE ZONE RECHARGE ZONE CATCHMENT AREA CATCHMENT AREA CONFINED ZONE NOT CONFINED ZONE

5. Hydrology 101

6. Seco Helicopter 2002 HEM Survey SENSOR SYSTEM  6 EM Frequencies 400 – 100,000 Hz  Internal Magnetometer  High Resolution GPS  Laser Altimeter

7. Geology with flight lines Geologic Map Showing Flight Lines 81 square miles 200 meter line spacing Red dot – sink hole Black USGS funding Red EAA funding

8. 100kHz Apparent Resistivity

9. 25kHz Apparent Resistivity

10. 6200Hz Apparent Resistivity

11. 1500Hz Apparent Resistivity

12. 400 Hz Apparent Resistivity

13. Depth section calculations UBC EM1DFM EMFLOW Differential Depth

14. Line 10240 Vertical Exaggeration ~x20 2000m 1 Mile 100m100m Trinity Group SinkholeSinkhole Del Rio Clay Edwards Group nothing SOUTH NORTH Geophysical structure correlation Mapped structure correlation SinkholeSinkhole

15. Geology with flight lines Geologic Map Showing Flight Lines 81 square miles 200 meter line spacing Red dot – sink hole Black USGS funding Red EAA funding

16. Line 10500 Resistivity depth section Vertical Exaggeration ~x10 2000m 1 Mile 200m200m Geophysical structure correlation Mapped structure correlation

17. STRUCTURAL MAPPING

18. STRATIGRAPHIC MAPPING

19. Final Pictures Project Funding Edwards Aquifer Authority: additional flying (50% increase) San Antonio Water System: electrical depth sections USGS: Geologic Discipline Water Resources Discipline

20. Line 10500 location