Abstract
While the benefits of determining the bulk density distribution of a landmass are evident, established experimental techniques reliant on gravity measurements cannot uniquely determine the underground density distribution. We address this problem by taking advantage of traffic tunnels densely distributed throughout the country. Cosmic ray muon flux is measured in the tunnels to determine the average density of each rock overburden. After analyzing the data collected from 146 observation points in Miura, South-Boso and South-Izu Peninsula, Japan as an example, we mapped out the shallow density distribution of an area of 1340 km2. We find a good agreement between muographically determined density distribution and geologic features as described in existing geological studies. The average shallow density distribution below each peninsula was determined with a great accuracy (less than ±0.8%). We also observed a significant reduction in density along fault lines and interpreted that as due to the presence of multiple cracks caused by mechanical stress during recurrent seismic events. We show that this new type of muography technique can be applied to estimate the terrain density and porosity distribution, thus determining more precise Bouguer reduction densities.
Highlights
While the benefits of determining the bulk density distribution of a landmass are evident, established experimental techniques reliant on gravity measurements cannot uniquely determine the underground density distribution
After analyzing the data collected from 146 observation points in Miura, South-Boso and South-Izu Peninsula, Japan as an example, we mapped out the shallow density distribution of an area of 1340 km[2]
The average shallow density distribution below each peninsula was determined with a great accuracy
Summary
While the benefits of determining the bulk density distribution of a landmass are evident, established experimental techniques reliant on gravity measurements cannot uniquely determine the underground density distribution. Muography can be utilized to monitor temporal density variations inside large objects, due to, e.g., magma dynamics[14] and underground water table changes[15], by taking advantage of the almost constant rate of muon flux arriving on Earth These measurements were all taken by placing a detector at a single location and by recording muon events there for several days (until obtaining the statistically sufficient amount). To calculate first the density length of the overburden X in units of m.w.e and the average density ,r., the theoretically predicted reduction factor I0/I is compared with the recorded muon counting rate ratio (called the observational reduction factor) N0/Nm between the data collected inside and outside of the tunnel along with the geometrical thickness of the target L (measured from, e.g., a topographic map). The time (t) required for holding the following equation: qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Â
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
