Multi-day radon signals with a radioactive decay limb -- occurrence and geophysical significance.
Multi-day signals, generally with duration of 2-10 days, are a prominent temporal variation type of radon (Rn) in geogas in the unsaturated zone. Rare multi-day Rn signals have been found which are characterized by: (a) a declining limb lasting up to 10 days which conforms to the radioactive decay of Rn, (b) recurs at the same location and (c) is recorded in diverse situations-volcanic and seismogenic. It suggested that a Rn blob is injected at a lower level on a steady upward flow of geogas whereby the rise and final fall of the signal are attributed to the edges of the blob while the central Rn-decay segment records the passing of the decaying blob itself. Rn-decay signals are a small subset of multi-day Rn signals which are considered as highly irregular and unusable for the understanding of geophysical processes. In difference, it is concluded that multi-day Rn signals are probably proxies of subtle geodynamic processes at upper crustal levels and are therefore significant for studying such processes.
Steinitz
G
G
Geological Survey of Israel, Jerusalem, Israel. steinitz@mail.gsi.gov.il
Martín
M C
MC
Gazit-Yaari
N
N
Quesada
M L
ML
de la Nuez
J
J
Casillas
R
R
Malik
U
U
Begin
Z B
ZB