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

2. Overview Overview of SuperGradiometer Installation
Introduction of Potassium dIdD
Summary and Conclusions

3. Overview of SuperGradiometer Installation
Instrumentation
SuperGradiometer Features
SuperGradiometer Array
UNAM-GEM Cooperation
Site Location, Selection and Data
Sensor Installation
Sample of Data Records
Sensor Field Inclinations and Declinations

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

5. 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

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

7. 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

8. Site Location: Oaxaca, Mexico

9. Site Location: Oaxaca, Mexico
Site of Mexican Supergrad is at latitude and longitude.

10. Site Location: Oaxaca, Mexico
El Trapiche San Francisco Cozoaltepec
Santa Maria Tonameca, Oaxaca

11. Site Selection: Survey
Overhauser Gradiometer Survey

12. Site Selection: Data
Gradiometric Survey Map
30 pT

13. Site Selection: Sensor Location

14. Sensor Installation: Pillars

15. Powering the System 14 Batteries = 420 Ah 23 Solar Panels = 920 watts

16. Data Transfer Upstream 300 Kbps Static IP Address
Currently upgrading to Satellite
Initial Setup with Local and Base (not shown) Towers

17. SG Total Field record pT

18. SG Gradient 12 hr

19. SG Gradients record pT

20. Sensor Field Inclination and Declination
Sensor 1: I = 43.16, D = 5.11º
Sensor 2: I = 43.12º, D = 5.05º
Sensor 3: I = 43.19º, D = 5.27º

21. Introduction of Potassium dIdD
Correction of Diurnals in Gradients & Israeli Experience
Potassium dIdD
Site Selection
Sensor Installation
Satellite View of Site
Experimental Results

22. Correction of Diurnals in Gradients & Israeli Experience
a) Difference G21= F2-F1
b) Difference G32= F3-F2
c) Y component of magnetic field
d) X component of magnetic field
e) Z component of magnetic field
Example of magnetic monitoring

23. Correction of Diurnals in Gradients & Israeli Experience
Leveled SuperGrad differences after ‘cleaning’
procedure.
a) Difference Gcorr21
b) Difference Gcorr32

24. Potassium dIdD 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 (maximum 5 readings per second, 15pT sensitivity at 1 reading per second).
Now, the dIdD has been enhanced significantly with the development of the Suspended dIdD system with potassium sensor.

25. Site Selection: Survey

26. Site Selection: Data
Gradient in dIdD 0.03 nT

27. Site Selection: Sensors Location
The distance from dIdD to:
Solar Panel            65 m
SG/CPU                  70 m
Sensor 1               150 m
Sensor 2               110 m
Sensor3                  80 m

28. dIdD Installation: Pillar

29. Satellite View of Site SG = SuperGrad console dIdD = dIdD system
S1 = Sensor 1
S2 = Sensor 2
S3 = Sensor 3
Solar= Solar panels and batteries

30. Experimental Results

31. Summary and Conclusions
We have tried to establish reference conditions to detect magnetic precursors of Earthquakes based on known precursors.
While trying to eliminate influence of diurnal variations of magnetic field, a need for a high sensitivity measurement of components arose.
We introduced a Potassium DIDD with some 15pT sensitivity, thus setting up possible new standards for a high sensitivity magnetic observatory