AEROMAGNETIC SURVEY
This is a continuation of the report of aeromagnetic surveys by the Hydrographic andOceanographic Department. The results of three surveys, Izu-Torishima, Nishinoshima andMiyake-jima carried out in 2011,2012, 2013 are presented in this report.
Key word: aeromagnetic survey.

1. Survey
The aircraft used for the survey was MA725(DHC-8). The aircraft was equipped with atail-stinger of non-magnetic plastics of 1.5 meters long at the rear of the fuselage. The instruments
used for the survey are a optical pumping magnetometer and GPS receiver.
The optical pumping magnetometer measured geomagnetic total intensity sampling rate 20Hz
with an accuracy of 0.01nT.

2. Data processing and results
The measured total intensity include components of external field variation. The correction of
the external field variation was carried out based on the continuous magnetic observations at areference magnetic observatory close to the survey area.
For calculations of magnetic anomaly, the IGRF2010 was used as the core field model inaccordance with the recommendation of the IAGA.
The details on the compiled aeromagnetic surveys are listed in Table 1.
Fig. 1~3 show the magnetic anomaly of the total intensity.
Reduction and compilation of this report have been made by K.Ogata,K.Onodera and K.Koyama
belong to Geodesy and Geophysics Office.

Reference
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.31, 1997,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.32, 1998,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.33, 1999,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.35, 2001,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.36, 2002,
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.37, 2003
Data Report of Hydrographic Observations, Series of Astronomy and Geodesy, No.38, 2004
AEROMAGNETIC SURVEY(2003-2008)
AEROMAGNETIC SURVEY(2009-2010)Table 1. Details on the compiled aeromagnetic surveys

Cruise index
Area
PeriodAircraft
Flight Altitude
Magnetometer

11TORI
Izu-Torishima
Nov. 15,17 2011

12NISI
Nishinoshima
Aug. 23 2012

MA725

MA725710m
ABOP-35(Opticalpumped310 mABOP-35(Opticalpumped

Potassiumom Magnetometer) Potassiumom Magnetometer)

Positioning
GPS
Track lines
0.5 naut. Mile N-S
Anomaly map
Fig. 1
Scale of original map
1/100,000
Map projection
TM
Reference Magnetic
KanoyaObservatory(31ﾟ25.’2 N, 130ﾟ52.’9 E)
Reference value for an
46,421 nT
External field correction
Core field model
IGRF2010
Contour interval
50nT
Epoch year
2011.11

Cruise index
Area
PeriodAircraft
Flight Altitude
Magnetometer

13MI
Miyake-jima
Jun.27 2013

MA725
1,525m
ABOP-35(Opticalpumped
Potassiumom Magnetometer)

Positioning
GPS
Track lines
0.25 naut. Mile N-S
Anomaly map
Fig. 3
Scale of original map
1/50,000
Map projection
TM
Reference MagneticKakioka
Observatory(36ﾟ13.'9 N, 140ﾟ11.'2 E)
Reference value for an
46,555 nT
External field correction
Core field model
IGRF2010
Contour interval
25nT
Epoch year
2013.6GPS
0.5~1 naut. Mile N-S
Fig. 2
1/100,000
TM
Chichijima(27ﾟ06.'0 N, 142ﾟ10.'8E)
41,120 nT
IGRF2010
50nT
2012.8－600+1336― ； >0― ； <0－‐－；＝0Kozu-shima

contour interval：50nT

Fig.1 Geomagnetic total intensity anomaly map in and around Izu-Torishima.
(Land area based on material Geographical Survey Institute)contour interval：50nT

Fig.2 Geomagnetic total intensity anomaly map in and around Nishinoshima.

contour interval：25nT

Fig.3 Geomagnetic total intensity anomaly map in and around Miyake-jima.
(Land area based on material Geographical Survey Institute)