Geophysical Exploration using Seismic Refraction to interpret geologic layers of the subsurface in the southeastern part of the Espanola Basin,

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Geophysical Exploration using Seismic Refraction
to interpret geologic layers of the subsurface in
the southeastern part of the Espanola Basin,
 SAGE 2001 Omar Abou-IsmailUniversity of
Utah
Picture Taken By Janet Yun

Many Thanks
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Geology of the Espanola Basin

• The Rio Grande Rift is a chain of interconnected
  asymmetric basins extended from central Colorado
  to Chihuahua Mexico.
• The Espanola Basin is part of the Rio Grande
  Rift, established 3-5 million years ago in
  northern New Mexico, consists of sedimentary and
  volcanic rocks of Eocene to Quaternary age
  (Manley). Major rifting occurred in the Espanola
  Basin during the late Cenozoic causing the
  thinning of the upper crust. The eastern part of
  the basin consists partly of the Precambrian
  southern rockies Sangre de Cristos Mountains.
  The western half consists of Jemez volcanic
  rocks. The La Bajada fault trends to the
  northwest with a displacement down to the
  southwest, separates the basin from the Santo
  Domingo subbasin to the south.
•                  

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This year geophysical work was done in the Santa
Fe Embayment portion of the Espanola Basin and
the north eastern part of the Albuquerque basin
(Santo Domingo basin).

• Seismic Refraction
• The length of the Seismic line is 3km.
• The receivers are 25m apart. Each array had 6
  geophones between the flag.
• Note Refraction surveys usually see 1/3 in depth
  of the length of the line.
• Sweeps are created by the Vibroseis Truck and
  data is collected.
• Sweeps vibrate at a frequency of 8-80hz and lasts
  approximately 8 seconds.

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Location Map
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Data Collected

1. Pick traveltime using recplt designed by Dr. John
   Ferguson.

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Before Record is picked we have to adjust the
trace gains to make the arrivals clearly
visible.Gains are specified in decibels (dB).6
dB is a factor of 2 in amplitude. So 6 or 12 dB
is approximately what we picked in order to check
for correct level.

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2. Travel time picks are then plotted by
Tadplt.
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Travel-time curves for basin (short offset)
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Travel time curves for long offsets
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3. Vision of models using modedt
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Shallow basin
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Deep refractors
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Interpretation of Basalt Layer
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T30.24 s
V34.3 km/s T20.13 s V21.84 km/s
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Total Amount of Offset 311m/4000,000y .078
mm/yrAverage elevation across spread C is 1683
m, and the top of the basalt cap of the mesa is
1829 m, subtract the elevations and add the depth
of the Basalt.

• 311 m Basalt Layer
  
• 165 m

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The EndMany thanks to all the Seismic
Refraction Team, Over