Scanning Inside Volcanoes with Synthetic Aperture Radar Echography Tomographic Doppler Imaging

Abstract

A problem with synthetic aperture radars (SARs) is that due to the poor penetrating action of electromagnetic waves within solid bodies, the ability to see through distributed targets is precluded. In this context, indeed, imaging is only possible for targets distributed on the scene surface. This work describes an imaging method based on the analysis of micro-motions present in volcanoes and generated by the Earth’s underground heat. Processing the coherent vibrational information embedded in a single SAR image, in the single-look-complex configuration, the sound information is exploited, penetrating tomographic imaging over a depth of about 3 km from the Earth’s surface. Measurement results are calculated by processing a single-look-complex image from the COSMO-SkyMed Second Generation satellite constellation of Vesuvius. Tomographic maps reveal the presence of the magma chamber, together with the main and the secondary volcanic conduits. This technique certainly paves the way for completely new exploitation of SAR images to scan inside the Earth’s surface.

Synthetic Aperture Radar Doppler Tomography Reveals Details of Undiscovered High-Resolution Internal Structure of the Great Pyramid of Giza

“…Multiple Doppler sub-apertures, SAR images with lower azimuth resolution, are generated to estimate the vibrational trend of some pixels of interest. The infra-chromatic displacement generated by Doppler centroid anomalies due to target motion and acceleration [65,66] is calculated through the pixel tracking technique, using high-performance sub-pixel coregistration [49,50,52,54,64].…”

“…Similarly, the complex structure number 9 identified immediately below the plane on which the pyramid rests has a shape similar to structures used to absorb the effects of mechanical vibrations that are transmitted through the ground [30]. The technique proposed in this article, unlike the classical SAR tomography developed in [52,64,65], has penetration properties orders of magnitude greater because what is proposed uses the vibrations (the phonons) and not the photonic information. A disadvantage of the present technique could be the processing time needed to carry out vibrational raw data synthesis, which requires substantial computing resources.…”

“…Problems connected to SAR acquisitions are that due to the poor penetrating action of electromagnetic waves within solid bodies, the ability to see through distributed targets is precluded. An imaging method based on the analysis of MMs present in volcanoes and generated by the Earth's underground seismic energy is described in [64], using penetrating tomographic imaging over a depth of about 3 km from the Earth's surface. The work describes also a complete assessment focused on showing the perfect space-time-frequency synchronization of SAR estimated vibrations with respect to seismic ripple estimated through in situ earthquake instruments.…”

Discussion of the Non-Destructive Testing Possibilities for the Study of the Great Pyramid of Giza

“…The measurement of vibrations, which generate the Doppler frequency shift of the reflected electromagnetic wave, has previously given rise to numerous areas of application and process research, such as the detection and remote diagnostics of people, including behind obstacles [44], humanitarian demining [45], the study of volcanic and seismic activity [46], as well as many others. Based on the results of measuring the surface vibration of the Great Pyramid, the authors of paper [43] describe the location of already known objects inside it, such as the chambers of the King and Queen, a Large Gallery, but also predict the existence of internal ramps, Figure 10.…”