“This is exactly what I studied geophysics for”

For EBN geophysicist Johannes van den Akker, the final months of 2025 were both the busiest and the most fascinating of his career. Operating from a temporary office at the farm of Cees Hogenhout in Ouderkerk aan de Amstel, he served as the central coordinator of the large-scale seismic survey conducted in Amsterdam and the surrounding area.

It was a major operation aimed at assessing the geothermal energy potential of the region, involving 20,000 recording devices, 140,000 information letters, numerous drilling rigs, seismic charges and nightly vibroseis surveys through the heart of Amsterdam.

The survey area covered a rectangle of approximately ten by sixteen kilometres across Amsterdam and its surrounding municipalities. More than half a million people live within the area, where geothermal energy could play a significant role in the sustainable heat supply of buildings. To determine the precise geothermal potential of the subsurface and identify promising locations for future geothermal developments, detailed seismic surveys first had to be carried out.

A large-scale operation delivered at speed

In September, Johannes and his colleagues, together with the field specialists from contractor Smart Seismic Solutions, began the field campaign. “Before Christmas, we were finished,” Johannes recalls. And yes, he acknowledges, that was fast.“We wanted to move quickly, but we also wanted to collect high-quality data. We were constantly looking for the right balance.”

A mosaic of subsurface data points

Johannes points to his computer screen, filled with dots, markers and grids spread across a map of Amsterdam and the surrounding area. At each of these locations, echoes of the subsurface were recorded. Sound waves were sent into the ground, reflected by geological layers and captured by small white-and-orange recording devices. At the peak of operations, Johannes estimates that around 120 people were working on the survey.

He acted as the project’s central coordinator and facilitator. “I spoke with the contractor about progress, with stakeholders such as residents, farmers and public authorities about permits and access, monitored safety, ensured financial control, kept the operation efficient and safeguarded data quality,” he explains.
“There was an enormous range of stakeholders, all of whom needed to understand exactly what we were planning.”

Shot-hole seismic surveying and other techniques

Different seismic techniques were used across the Amsterdam metropolitan region. To obtain the highest-quality subsurface data in rural areas, the team placed seismic charges at a depth of 20 metres using long tubes inserted by a small drilling rig mounted on a tractor. The charges were then detonated. This technique is known as shot-hole seismic surveying.
“For open countryside, meadows and agricultural land, it is the ideal technique,” says Johannes.“Of course, we needed the cooperation of local farmers, around 300 in total. Fortunately, that process went smoothly.”

A geothermal energy supporter

One of those farmers is a strong supporter of geothermal energy: Cees Hogenhout from Ouderkerk aan de Amstel. He had previously made his land available as a drilling location. In the autumn of 2025, he again offered space on his property, this time for the temporary office supporting the seismic survey. The site became a substantial operational hub, with office units and parking facilities for project staff. Johannes laughs: “Try renting an office of that size in Amsterdam at a reasonable price. We’re fortunate to have geothermal energy supporters like farmer Cees.”

Through the heart of Amsterdam

For surveys in the more sensitive and densely built-up city centre, with its historic canal houses, monuments and quay walls, a different method was required. Specialised trucks fitted with vibration plates underneath, known as vibroseis vehicles, were deployed. Often during the night, these vehicles travelled throughout the city, stopping every 20 metres to send controlled vibrations into the subsurface and record the returning signals. They would vibrate for about a minute and then continue to the next location. The distinctive convoy travelled across Dam Square, through narrow streets and along the canals of Amsterdam after dark.

Addressing concerns and questions

“This kind of operation does not go unnoticed. People can wake up because of it. And people did wake up because of it,” the geophysicist says. For that reason, local residents were informed extensively throughout the project. Approximately 140,000 information letters were distributed. A dedicated complaints and damage protocol was established, and a telephone line was available around the clock. And questions certainly came in. Some residents emailed messages in capital letters saying things like: ‘Take your vibration truck somewhere else.’ Johannes understands their reaction. “It makes sense. If a vibrating truck is standing outside your front door in the middle of the night, you wake up concerned and perhaps you don’t immediately remember all the details from the SCAN information letter.”

Some residents preferred to discuss their concerns by telephone. The contractor and survey team were happy to do so. “We explained what we were doing and how long the work would continue. Then we could tell the more positive part of the story: that we are doing this to support the development of geothermal energy in the region.” According to Johannes, more than 90 per cent of residents, regardless of background, were understanding of the work. On occasions when local sentiment in a particular street proved more negative, the team could simply postpone work there and return at a later stage.

Enjoying time in the field

Because of his responsibilities, Johannes spent less time in the field than earlier in his career, when he was more directly involved in the operational side of seismic surveys. “Whenever possible, I still tried to get out into the field. It allowed me to monitor safety and quality, and it’s simply enjoyable to work alongside the survey crews.”

Fascinating and intense

Looking back, Johannes describes the project as both “extremely interesting” and “extremely stressful”. The days were long. “And when the night-time work across the city begins, you’re naturally alert as well.” The combination of activities, complexity, scale, pace and responsibility made the project uniquely rewarding.

“This is exactly what I studied geophysics for.”

As if the project itself was not demanding enough, Johannes also became a father in late October, right in the middle of the survey programme.
Smiling, he points out one advantage: “When our newborn son was awake in the middle of the night trying to find his rhythm, I could immediately check my phone to see whether there was any news from the vibroseis crews.”

Collecting and analysing the data

All seismic data have now been collected. “I’m very satisfied with how the survey was carried out,” Johannes concludes. In general, the area around Amsterdam does appear to offer opportunities for geothermal energy development. However, the definitive results are still to come.
His colleague and namesake, Johannes Rehling, is now responsible for managing the vast quantity of data generated by the survey. Over the coming months, information from all 20,000 recording devices will be categorised, processed and analysed to provide a detailed picture of the subsurface and its geothermal energy potential.