# Presentation: 727424

## Seismic Reflection

- San Marcos Archeological Site
- Emily Pangborn

## Objective:  Image N 18  Kivas

## Reflection Line Setup

- 48 channel spread
- 0.25 m geophone interval
- 0.25 m shot point interval
- Maximum fold of 24
- 169 shot points
- 25 shot walk-on (first 6 m)
- Split spread from 6-42 m

## Equipment

- Bison 9048 recorder
- 100 Hz geophones
- Source:  Estwing rock hammer striking a  15 x 15 x 2.5 cm aluminum plate
- Roll switch 96 to 48 channels

## Sampling Interval

- Sampling Interval = 0.0001 s
- Sampling Frequency = 10000 Hz
- Nyquist Frequency = 1 / (2 x Δ t)                                         	                          = 5000 Hz

## Initial Reflection Images

***Figure1 - Constant velocity of ***
***300 m/s, 10 ms gain***

***Figure 2 - Constant velocity of 300 m/s, 20 ms gain***

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- CMP LOC

- Time (ms)

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- 0

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- CMP LOC

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- Time (ms)

## SAGE 2004 Refraction Model

## Constant Velocity Adjustments

***Figure 3 - Constant stacking velocity of 200m/s***

***Figure 4 - Constant stacking velocity of 350m/s***

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- CMP LOC

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- Time (ms)

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- Time (ms)

- CMP LOC

## Upper Limit Frequency Changes

***Figure 5 - Upper Frequency Limit of 1000 HZ ***

***Figure 6 - Upper Frequency Limit of 1500 HZ***

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- 200            240            280          320          360

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- CMP LOC

- CMP LOC

- Time (ms)

- Time (ms)

## Implementation of Velocity Function

***Figure 7 - Velocity function ***

***Figure 8 - Velocity function appearing in flow chart***

## Amplitude Scaling

***Figure 9 – Scaled by largest Amplitude***

***Figure 10 -  Scaled in 16 ms Sliding Window (AGC)***

## Scaling by Largest Amplitude 

***Figure11 – Profile with largest amplitude scaling and applied velocity function***

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- CMP LOC

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- Time (ms)

## Scaling in 16 ms Window

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- CMP LOC

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- Time (ms)

***Figure12 – Profile with 16 ms window scaling and applied velocity function***

## Mixed Traces – Scaling by Largest Amplitude 

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- Time (ms)

- CMP LOC

***Figure13 - Profile with largest amplitude scaling.  Traces weighted and averaged in groups of three. ***

## Mixed Traces - Scaling in16 ms Window

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- 0

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- Time (ms)

- CMP LOC

***Figure 14 – Profile with AGC scaling.  Traces are weighted and averaged in groups of three.***

## Conclusions

- Strong reflections corresponding to kivas at depths 1.5 – 2 m
- Reflection at 25 ms corresponding to
-    2000 m/s site “basement” (Galisteo formation?)