Post on 01-Apr-2015
New Magnetic Observatory Installation
In Oaxaca, Mexico
IAGA 2008Golden, Colorado, USA
Ivan Hrvoic, Enrique Cabral, Esteban Hernandez, Gerardo Cifuentes, Mike Wilson, Francisco Lopez
Overview
• Overview of SuperGradiometer Installation
• Introduction of Potassium dIdD
• Summary and Conclusions
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
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
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
• 3 sensors arranged according to terrain (horizontal or vertical)
• Sensor spacing up to 140m• Long term integration is promising
SuperGradiometer Array
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
Site Location: Oaxaca, Mexico
Site Location: Oaxaca, Mexico
Site of Mexican Supergrad is at 1751171 latitude and 745773 longitude.
Site Location: Oaxaca, Mexico
El Trapiche San Francisco CozoaltepecSanta Maria Tonameca, Oaxaca
Site Selection: Survey
Overhauser Gradiometer Survey
Site Selection: Data
30 pT
Gradiometric Survey Map
Site Selection: Sensor Location
Sensor Installation: Pillars
Powering the System
14 Batteries = 420 Ah
23 Solar Panels = 920 watts
(38 Ah)
Data Transfer
Upstream 300 Kbps
Static IP Address
Initial Setup with Local and Base (not shown) Towers
Currently upgrading to Satellite
• SG Total Field record
39045400
39045600
39045800
39046000
39046200
39046400
39046600
39046800
39047000
39047200
39047400
39047600
39047800
39048000
39048200
39048400
39048600
39048800
39049000
39049200
39049400
39049600
39049800
39050000
39050200
39050400
pT
• SG Gradient 12 hr
• SG Gradients record
21040
21045
21050
21055
21060
21065
21070
21075
21080
21085
21090
21095
21100
21105
21110
21115
21120
pT
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
Introduction of Potassium dIdD
– Correction of Diurnals in Gradients & Israeli Experience
– Potassium dIdD– Site Selection– Sensor Installation– Satellite View of Site– Experimental Results
Correction of Diurnals in Gradients& Israeli Experience
Example of magnetic monitoring
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
Correction of Diurnals in Gradients& Israeli Experience
Leveled SuperGrad differences after ‘cleaning’ procedure.a) Difference Gcorr21b) Difference Gcorr32
Potassium dIdD GSMP-35 dIdDIn 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.
Site Selection: Survey
Site Selection: Data
Gradient in dIdD 0.03 nT
Site Selection: Sensors Location
The distance from dIdD to:Solar Panel 65 mSG/CPU 70 mSensor 1 150 mSensor 2 110 mSensor3 80 m
dIdD Installation: Pillar
Satellite View of Site
SG = SuperGrad consoledIdD = dIdD systemS1 = Sensor 1S2 = Sensor 2S3 = Sensor 3Solar= Solar panels and batteries
Experimental Results
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