A strong-motion accelerograph, an instrument used to measure the accelerations due to earthquake waves shaking the ground or structures. The accompanying record was of the Helena, Montana earthquake of October 31, 1935. In: Bulletin of the Geological Society of America, Vol. 49., No. 1, pp. 1-21.

Overhead view of a Coast and Geodetic Survey strong-motion accelerograph.

A vibration meter for recording building and ground vibrations.

Earthquake epicenters off the West Coast of the United States and Mexico as observed through early 1927.

Earthquake epicenters in the Western and Northern Pacific Ocean as of early 1927

The correlation of high seismicity with the Mid-Atlantic Ridge. This map was produced in 1937. Note the refinement of earthquake zones on this map as compared to the map in image cgs02176. In: Proceedings of the American Philosophical Society, Vol. 79, No. 1, Symposium on the Exploration of the Ocean Bottom Arranged by the American Geophysical Union (April 21, 1938), pp. 97-108.

The correlation of high seismicity with what is now known as the Gakkel Ridge, a segment of the mid-ocean ridge system. In: Proceedings of the American Philosophical Society, Vol. 79, No. 1, Symposium on the Exploration of the Ocean Bottom Arranged by the American Geophysical Union (April 21, 1938), pp. 97-108. The first hint that the Mid-Atlantic Ridge continued through the Arctic Ocean.

"Earthquake Zones", world seismicity map clearly showing the correlation of the Pacific Ring of Fire with earthquake epicenters, the Alpine-Himalayan Belt, and the coincidence of major portions of the mid-ocean ridge system with areas of seismicity. Map published in The Geographical Review, Vol. XXV, No. 1, 1935, Pl. 1.

A median section through the earth showing composition of the interior and transmission of earthquake waves. In: Earthquakes and Astronomy" by N. H. Heck. Published in: The Sky, March 1937. P. 14.

Newly uplifted seafloor along fault-line in SE Alaska. The beach was elevated 47 feet 4 inches on the west side of Disenchantment Bay. Yakutat Bay earthquake of September 1899.

Japanese fishing vessel thrown ashore by tsunami accompanying earthquake of March 7, 1933, on the Sanriku coast of Japan.

A magnetic instrument. The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

A magnetic instrument The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

The Sine galvanometer

A magnetic instrument The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Magnetic instruments The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Various magnetic instruments The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Operating magnetic instruments The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

A magnetic instrument The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Observatory magnetometer Ruska type

Observatory magnetometer Ruska type

Magnetic instrumentation. The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Magnetic instrumentation. The Coast and Geodetic Survey was the Nation's primary geophysical agency until the early 1970's when its geomagnetic duties were transferred to the USGS.

Observatory magnetometer Ruska type

Observatory magnetometer Ruska type

Magnetic instrumentation.

Magnetic instrumentation.

Magnetic instrumentation.

Observatory magnetometer Ruska type

Horizontal intensity variometers.

Horizontal intensity variometers on left

Coil assembly and sensor for automatic standard magnetic observatory

Coil assembly and sensor for automatic standard magnetic observatory

Magnetic instrumentation.

Coil assembly for automatic standard magnetic observatory

Coil assembly for automatic standard magnetic observatory

Coil assembly for automatic standard magnetic observatory

Coil assembly for automatic standard magnetic observatory

Magnetic instrumentation.

Automatic scaling system for scaling magnetograms.

Automatic scaling system for scaling magnetograms.

Automatic scaling system for scaling magnetograms.

Automatic scaling system for scaling magnetograms.

Hand-scaling of magnetograms.

Hand-scaling of magnetograms.

Automatic scaling system for scaling magnetograms.

Components of an automated magnetic observatory

Components of an automated magnetic observatory

Components of an automated magnetic observatory

Components of an automated magnetic observatory