Trucks send seismic waves beneath cities to explore the terrain for oil, gas, faults and geothermal.

In 2017, two fleets of massive trucks crossed from Long Beach into Orange County in southern California, sending literal shock waves through the streets. And now, in Germany, they're going to be at it again.

The vehicle used to create these vibrations is a seismic vibrator truck or thumper. These trucks use a large weight to thump the ground's surface while sophisticated equipment reads and records the reverberating waves. The time of arrival of each wave creates a picture of the subsurface.

According to Tracey Farmer, spokesman for LA Seismic, the Signal Hill-based company that conducted the project, the California thumpers were just collecting readings for any interested party to buy. "We're data collectors. We're self-funded. We do this in hopes that companies will buy our data."

Trucks like these deploy thumping devices that send seismic waves beneath landscapes to explore the terrain for gas, oil, faults or geothermal. They're used for safety, city planning, resource development and any other interest in seeing what's going on underfoot before digging.

"We work in cooperation with USGS and Cal Tech," said Farmer. "They can take our data and create a 3-D picture that cities can then use to find previously unknown faults. It's part of the agreement we make with cities we survey, to make this data available to them."

The Continental Oil Company developed the Vibroseis exploration technique back in the 1950s. Today, seismic vibrators are used to perform about half of all seismic surveys on land.

Predominantly used in the oil and gas industries, these hardy seismometers on wheels are now looking into city geothermals in hopes of finding some free energy.

H2: Enhanced geothermal

The basic idea of manmade geothermal energy (called enhanced geothermal) is similar to steam power – you shoot water deep into the earth's crust, where it's naturally hot, which returns to the surface and powers a turbine to generate electricity. This could add ready-made green energy to areas whose locations otherwise don't lend themselves to other forms of energy like solar or wind.

Geothermal development company Fervo Energy has developed a cutting-edge method of drilling geothermal wells that shave 70% off drilling times (as fast as 21 days) and is 50% cheaper (around four million dollars from nine.) Fervo drilled its first horizontal well in Nevada as part of a Google-backed advanced geothermal plant.

While it's a clean and renewable way to produce power, finding areas where both underground heat sources and geology are suitable for such a use can be challenging, especially in already built-up areas like big cities.

Urban Vibro

Enter the Urban Vibro Trucks built by Herrenknecht AG, a German company that specializes in underground tunneling technology. The trucks are being developed in collaboration with the Geophysical Institute of the Karlsruhe Institute of Technology (KIT).

Each truck is equipped with smart safety features, including a collision-awareness system and birds-eye-view camera system. They ride on eight wheels with all-wheel-drive, allowing for exceptional maneuverability on city streets. Weighing in at around 32 tons, these trucks can reach a top speed of roughly 40 kilometers per hour (25 miles per hour).

The trucks deploy a thumper device known as a P-wave shaker from beneath the vehicles. This shaker sends seismic waves into the ground beneath it, and a grid network of geophone sensors on the surface records the reflected waves, providing a detailed map of the underground environment, which is expected to present enough data to bring geothermal systems into urban settings.

"The German government plans to identify up to 100 potential sites for geothermal energy," Herrenknecht's Axel Langer told New Atlas. "Many campaigns currently fail due to lengthy and complicated regulatory procedures. With our truck, these hurdles would be significantly reduced, as it resembles a municipal vehicle and is therefore better suited for urban environments."

The thumpers are expected to undergo testing in collaboration with KIT in June, followed by the deployment of a prototype vehicle in the last quarter of this year. If successful, serial production of the trucks may take place as early as 2025.

Anticipate more of these thumpers in your neck of the woods as urbanization spreads and governments push for more sustainable power and domestic resources – perhaps even closer to home than expected.

You can watch the trucks work in Herrenknecht's promo video.