New Magnetic Observatory Installation

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• New Magnetic Observatory Installation
• In Oaxaca, Mexico
• IAGA 2008Golden, Colorado, USA Ivan Hrvoic,
  Enrique Cabral, Esteban Hernandez, Gerardo
  Cifuentes, Michael Wilson, Francisco Lopez

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Overview

• Overview of SuperGradiometer Installation
• Introduction of Potassium dIdD
• Summary and Conclusions

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Overview of SuperGradiometer Installation

• Instrumentation
• SuperGradiometer Features
• SuperGradiometer Array
• UNAM-GEM Cooperation
• Site Location Oaxaca, Mexico
• SuperGrad Sensor Locations
• Installation
• Pillars
• Powering System
• Data Transfer
• Sample Records
• Total Fields
• Gradients
• Field Inclinations and Declinations

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Instrumentation

• Most Sensitive Scalar Magnetometer
• Based on Optically Pumped Potassium
• High sampling (up to 20 samples / second)
• Designed for minimal heading error, high absolute
  accuracy and reliability

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SuperGradiometer Features

• Delivers sensitivity needed for Short Base or
  Gradiometric work in Earthquake Studies
• Background noise is 50 fT for 1 reading / second
• Can increase sensitivity further by placing
  sensors at specific distances, say 50 to 100m,
  which gives 1 fT/m gradient sensitivity

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SuperGradiometer Array

• 3 sensors arranged according to terrain
  (horizontal or vertical)
• Sensor spacing up to 140m
• Long term integration is promising

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UNAM-GEM Cooperation

• Geophysics Department of UNAM expressed interest
  in deployment in Mexico
• Discussions about experimental deployment of
  SuperGradiometer for Earthquake studies
• Site selection possibilities

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Site Location Oaxaca, Mexico
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SuperGrad Sensor Locations
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Installation Pillars
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Installation Powering the System
14 Batteries 420 Ah 23 Solar Panels 920 watts

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Installation Data Transfer
Real-time data transfer and full remote control
via Satellite link
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• Sample Data Set Total Fields _at_ 1Hz

4nT/div
CH3
Total Field
CH1
CH2
June 1st 2008 24Hr data
June 1st 2008 24hr period
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• Sample Data SetGradients _at_ 1Hz

20pT/div
CH2-CH1
CH3-CH2
June 1st 2008 24hr period
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Field Inclination and Declination

• Main Pillar I 43.31 º D 5.33º
• Sensor 1 I 43.24º, D 5.13º
• Sensor 2 I 43.14º, D 5.34º
• Sensor 3 I 43.36º, D 5.38º

Measurement May 2008
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Introduction of Potassium dIdD

• Potassium dIdD
• Site Selection
• Survey
• Data
• Sensor Locations
• Satellite View of Site
• Sensor Installation
• Pillar and Initial Setup
• Bias and Final Adjustments
• Preliminary k-dIdD Results
• Preliminary Correction of SuperGrad Gradient data

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GSMP-35 dIdD

• In the past, some magnetic observatories relied
  on a combination of Overhauser dIdD, and
  theodolite instruments for obtaining
  measurements.
• GEM introduces new GSMP-35 dIdD (delta
  Inclination / delta Declination) system for high
  precision results (standard 20 readings per
  second - 4 dIdD cycles per second), 5pT
  sensitivity at 1 reading per second dIdD mode.
• Now, the dIdD has been enhanced significantly
  with the development of the Suspended dIdD system
  with potassium sensor.

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Site Selection Survey
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Site Selection Data
Gradient in dIdD 0.03 nT/m
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Site Selection Sensor Locations
The distance from dIdD to Solar Panel   65
m SG/CPU                  70 m Sensor
1               150 m Sensor 2               110
m Sensor3                  80 m
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Satellite View of Site
SG SuperGrad console dIdD dIdD system S1
Sensor 1 S2 Sensor 2 S3 Sensor 3 Solar Solar
panels and batteries
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Potassium dIdD Installation Pillar Initial
Setup
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Potassium dIdD InstallationBias and final
adjustments
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Preliminary k-dIdD Results
nT
X
Y
Z
dIdD Total Field
June 1st 2008 24hr period
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Preliminary Correction of SuperGrad Gradient Data
5pT/div
CH2 CH1 uncorrected
CH2-CH1 corrected using k-dIdD results
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Summary and Conclusions

• We have tried to establish reference conditions
  to detect magnetic precursors of Earthquakes
  based on known precursors. This is still in
  progress.
• High sensitivity measurement of components arose,
  in an attempt to reduce invasion of diurnal
  changes in gradient records
• Focus is now shifting to a high resolution
  magnetic observatory

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Summary and Conclusions

• We introduced a Potassium dIdD with some 5pT at
  1Hz sensitivity, thus setting up a possible new
  standard for a high sensitivity magnetic
  observatory.
• Further analysis of data is underway.