70 Years of Seismology at DTM Shaun Hardy and Louis Brown Carnegie Institution for Science Neighborhood Lecture Series April 25, 2019

1948 DTM seismic truck with instruments for recording waves from “artificial earthquakes.” Controlled explosions were set off across the Mid-Atlantic region to probe Earth’s crust.

1948 Hypothetical crustal structure beneath Washington DC from DTM’s earliest explosion seismology experiments.

1951 Detonation of depth charge from a Coast Guard cutter in Puget Sound during joint DTM-GL seismic experiment.

1955 Seismic equipment set up on a railroad flatcar during DTM’s seismic expedition to Alaska and Yukon Territory.

1957 Truck with seismic equipment and radio receiver deployed in Peru during the Carnegie Andes Expedition.

1957 Explosion set off in an open-pit copper mine in Peru for Carnegie’s seismological studies of the Andes during the International Geophysical Year.

1960 DTM cooperative seismic network for the study of local earthquakes. Nineteen stations were installed in Peru, Bolivia, and Chile.

1962 Short-period vertical seismograph designed by DTM for use in South American seismic network. Data could be recorded for up to one week without intervention.

1963 DTM-built horizontal-motion seismometer used in South American seismic network.

1963 South American scientists at DTM for a 2-month long intensive seminar determine earthquake epicenters using a “ping-pong table” analog computer.

1966 First broad-band, large dynamic range seismometer designed at DTM by Selwyn Sacks.

1971 Alan Linde, Selwyn Sacks, and Shigeji Suyehiro search for seismic events on DTM broadband seismograph tapes.

1971 Selwyn Sacks, Shigeji Suyehiro, and Michael Seemann assemble a borehole strainmeter – a device developed by Sacks and Dale Evertson for measuring minute deformation in the Earth.

1970s Installing DTM borehole strainmeters at Matsushiro Observatory, Japan (1971) and 3.2 km underground in a South African gold mine (1978).

1978 Strain record of a “slow” earthquake sequence in Japan – undetectable with seismometers but recorded by DTM borehole strainmeters (Alan Linde et al.)

1994 DTM’s Paul Silver (shown here in Bolivia) and colleagues pioneered the deployment of modern, portable broadband seismic arrays.

1990s South Africa 1997 Iceland 1995 Zimbabwe 1997 South Africa 1998 Galapagos 2000 Brazil 1993 Broadband seismometer installations around the world by DTM scientists and collaborators.

1997 Mantle plume beneath Iceland imaged by seismic tomography from the ICEMELT experiment (Cecily Wolfe et al.)

1997 “Huddle test” of 40 three-component broadband seismometers in DTM testing facility (Rod Green, Randy Kuehnel, Adriana Kuehnel)

1997 1800-km long seismic array for study of the deep structure of the Kaapvaal Craton in southern Africa (David James, Paul Silver, et al.)

2014 Diana Roman deploys a BENTO2 seismic-monitoring box at Hekla Volcano, Iceland. Satellite telemetry enables continuous monitoring of volcanoes in remote areas.

2016 Lara Wagner with a Carnegie Quick Deploy Box (QDB) – a new, portable broadband seismometer small and light enough to be checked as airline luggage.

2019 DTM field seismologist Steven Golden tests a new broadband seismometer for array deployment on Vanuatu.