Portable seismological equipment

Coast and Geodetic Survey seismologist communicating with colleague

Coast and Geodetic Survey seismologist communicating with colleague

Coast and Geodetic Survey seismologist plotting earthquake epicenter with spacing dividers

Coast and Geodetic Survey seismologist plotting earthquake epicenter

Coast and Geodetic Survey seismologist obtaining data to plot earthquake epicenter

Coast and Geodetic Survey seismologists at work

Lieutenant Philip Taetz at desk. Possibly Honolulu Observatory.

Benioff horizontal seismometer

Benioff horizontal seismometer

Seismograph - spgr.

Seismograph - spgr.

Diagram of a type of seismometer

World Wide Standardized Seismological Network Galvos

World Wide Standardized Seismological Network Galvos

World Wide Standardized Seismological Network Galvos

Structure of Coast and Geodetic Survey Office of Seismology and Geomagnetism

What the Geomagnetism Branch of the Coast and Geodetic Survey did

Products of the Coast and Geodetic Survey Geomagnetism Program

An artist's conception of the Earth's structure and geomagnetic field

Geomagnetic observatories that were currently putting hourly values in machine- readable form as of 1969.

Geomagnetic observatories that were putting hourly values in machine-readable form prior to the International Geophysical Year.

Geomagnetic observatories with digital magnetometers as of 1969.

Geogmagnetic observatories that have facilities for semi-automatic scaling of magnetogram records as of 1969.

Compass rose for use by mariners in comparing magnetic direction with true direction.

Magnetogram plots.

Magnetogram plots.

United States repeating stations as of 1969

Edmund Halley's isogonic chart of 1701 showing lines of equal magnetic declination. This was the earliest chart of this nature and one of the earliest geophysical thematic maps.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveying operations associated with determination of magnetic declination.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Surveyor taking sun azimuth for true direction to determine magnetic declination from magnetic observations.

Observer operating field-type Ruska magnetometer.

Observer operating field-type Ruska magnetometer.

Calibrating geomagnetic instruments at the Coast and Geodetic Survey geomagnetic observatory at Corbin, Virginia.

Calibrating geomagnetic instruments at the Coast and Geodetic Survey geomagnetic observatory at Corbin, Virginia.

Administrative Building at Fredericksburg Geomagnetic Observatory

Honolulu Geophysical Observatory

Honolulu Geophysical Observatory

Honolulu Geophysical Observatory. The vault?

Honolulu Geophysical Observatory

College, Alaska, seismic and magnetic observatory

College, Alaska, magnetic observatory

Quartz horizontal magnetometer

Quartz horizontal magnetometer

Universal gravitometer (synonymous with gravity meter - not in the sense of an instrument to measure specific gravity)

Universal gravitometer (synonymous with gravity meter - not in the sense of an instrument to measure specific gravity)

A seismograph record of the Long Beach Earthquake of March 10, 1933.