Anyone who wants to take a look inside the Earth needs a signal that can penetrate rocks, minerals and other opaque material. Seismic waves represent such a signal. If you record them with a seismometer, you can draw conclusions from the recorded data about the state of the subsurface through which the waves have passed.

Knowledge of subsurface stress or strain fluctuations is just as important for safety in construction and mining, for example, as it is for monitoring geological processes in volcanoes and fault zones.

Now Christoph Sens-Schonfelder from the GFZ German Research Centre for Geosciences in Potsdam and Tom Eulenfeld from the University of Jena have been able to show that the seismic waves excited by the surf, together with the effect of the Earth's tides on the subsoil, can be used to better understand the properties of the Earth.

Seismic waves not only provide information about the structure of the Earth's material, but also about the forces acting on it. For example, deformations of the subsurface change the velocity at which a wave travels.

In order to draw conclusions about the subsurface forces from the velocity, however, data is required on how the material reacts to deformations under known conditions. Until now, such data have only been available from laboratory experiments, not from the field.

Christoph Sens-Schonfelder and Tom Eulenfeld have now succeeded for the first time in using a single seismometer to measure how sensitively seismic waves react to the deformation of the Earth's material they propagate in. In order to achieve that, they evaluated the velocity of the seismic noise generated by the surf. They report on this in the journal Physical Review Letters.

Measuring deformations in the Earth's interior from the surface
"We use two different signals that the environment provides us with naturally," explains Christoph Sens-Schonfelder. "Due to the tidal effect of the moon and the sun, the universe conducts a permanent deformation experiment with the Earth. The luminaries pull with great regularity on our planet. To observe this pulling, we use the seismic noise in the underground that is generated by the surf."

The relation investigated by Christoph Sens-Schonfelder and Tom Eulenfeld allows in principle a measurement of the deformations inside the Earth by means of recordings of seismographs on the Earth's surface. And that without having to drill into the ground.

The data that the two researchers investigated was recorded by the Integrated Plate Boundary Observatory in the Atacama Desert in northern Chile. Improved software was needed to detect even the slightest changes in wave velocity and to combine these changes with the deformation of the subsurface by the tides. Since this tidal deformation is known with high accuracy, it is possible to characterize the subsurface more comprehensively than before.

Related Links
GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Earth Observation News - Suppiliers, Technology and Application

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Land-cover dynamics unveiled
Paris (ESA) Mar 22, 2019
Billions of image pixels recorded by the Copernicus Sentinel-2 mission have been used to generate a high-resolution map of land-cover dynamics across Earth's landmasses. This map also depicts the month of the peak of vegetation and gives new insight into land productivity. Using three years' worth of optical data, the map can indicate the time of vegetation peak and variability of vegetation across seasons. Developed by GeoVille, an Austrian company specialised in the analysis of satellite data, t ... read more