Authors:W. Plastino, G. Panza, C. Doglioni, M. Frezzotti, A. Peccerillo, P. De Felice, F. Bella, P. Povinec, S. Nisi, L. Ioannucci, P. Aprili, M. Balata, M. Cozzella, and M. Laubenstein
The ability to predict earthquakes is one of the greatest challenges for Earth Sciences. Radon has been suggested as one possible
precursor, and its groundwater anomalies associated with earthquakes and water–rock interactions were proposed in several
seismogenic areas worldwide as due to possible transport of radon through microfractures, or due to crustal gas fluxes along
active faults. However, the use of radon as a possible earthquake’s precursor is not clearly linked to crustal deformation.
It is shown in this paper that uranium groundwater anomalies, which were observed in cataclastic rocks crossing the underground
Gran Sasso National Laboratory, can be used as a possible strain meter in domains where continental lithosphere is subducted.
Measurements evidence clear, sharp anomalies from July, 2008 to the end of March, 2009, related to a preparation phase of
the seismic swarm, which occurred near L’Aquila, Italy, from October, 2008 to April, 2009. On April 6th, 2009 an earthquake
(Mw = 6.3) occurred at 01:33 UT in the same area, with normal faulting on a NW–SE oriented structure about 15 km long, dipping
toward SW. In the framework of the geophysical and geochemical models of the area, these measurements indicate that uranium
may be used as a possible strain meter in extensional tectonic settings similar to those where the L’Aquila earthquake occurred.
Due to the subcrustal earthquakes located at the sharp bend of the Southeast Carpathians, Vrancea zone in Romania has a high
potential seismic hazard in Europe. Among several seismic precursors, radon anomalies in air, ground, and groundwater in the
epicentral areas can be associated with the strain stress changes that occurred before and after earthquakes. In order to
support this theoretical view, the main aim of this paper was to investigate temporal variations of radon concentration levels
in air near the ground and in ground air by the use of solid state nuclear track detectors CR-39 and LR-115 in relation with
some seismic events at two seismic stations Vrancioaia and Plostina, located in Vrancea active region. This paper reports
essentially the observation of radon concentration levels in the air near the ground at 1 m height for the earthquakes that
occurred during the period of November 2010–October 2011 and moment magnitudes Mw in the range of
. The average radon concentration in air above the ground measured with CR-39 detectors recorded for 1 year period in Vrancea
area was 1,094.58 ± 150.3 Bq/m3 and 10 days fluctuations were placed in the range of 129 ± 40 Bq/m3 and 5,888 ± 700 Bq/m3. Also have been reported measurements of in soil radon concentrations in drill holes at 0.5 m depths during period of March
1977–October 1980, just after 4 March 1977, Mw 7.4 Vrancea earthquake. The knowledge of air–ground–gas 222Rn anomalies is very important for earthquake pre-signals assessment as well as for precisely location of geologic active
Authors:L. L. A. Vermeersen, R. Riva, and R. Sabadini
The 3D quasi-static displacements during and following an earthquake provide a wealth of information on the internal structure and rheological properties of the Earth. If an earthquake occurs in a region that has shallow-viscosity zones inside the crust or at the top of the mantle (asthenosphere), then post-seismic displacements of the crust on the order of millimeters per year are possible. These can be detected by means of permanent GPS stations in the years following a faulting event. In this paper we systematically study the influence of viscoelastic simulation model restrictions on co- and post-seismic deformation. Examples include stratification of the Earth model, modeling of the seismic source, influence of compressibility, effects of position and viscosities of shallow low-viscosity layers. It will be shown that some of these model restrictions or assumptions can have non-negligible influences on the simulated 3D co- and post-seismic displacements.
The understanding of fracture has tended to follow great public disasters (e.g. over 200 US ships suffered due to catastrophic failure during WW II, later several jet air-craft damaged, destroying some bridges and buildings, etc). Rock fracture mechanics dates back to early 60-s and its application to rock blast problems, collapses deep gold mines in South Africa, earthquake disasters, etc. Pure shear mode (Mode I) or mixed tension and shear mode (Mode I and II) fracturing are the most important in rock mechanics and geophysics. The goal of this paper is to summarize the existing fracture criteria and the observed crack growth firstly from single flaws, secondly from multiply (two) flaws. Analysing the fracture propagations different types of coalescence can be determined and classified. Using these modelling and analysing the observed patterns, for example we could forecast the new failures after the earthquakes or calculating the stability of rock slopes, etc.
The purpose of this work is to investigate how the local soil conditions in the Bucharest area control the ground motion characteristics using all the available acceleration data for large and moderate size Vrancea earthquakes. The proposed comparative analysis shows no systematic variations from one site to the other in agreement with the relatively uniform subsurface structure beneath the city. The main conclusion of this study is that for the particular case of Bucharest and Vrancea earthquakes, basically the microzonation is emphasizing no areas with significant variation in the amplification factor. At the same time, the source radiation is clearly controlling the seismic response depending on the magnitude. Thus, for the largest shocks (Mw ≯ 7), the seismic response in the range of 1-2 s period is exceptionally enhanced leading to the disastrous damage noticed for the high-tall buildings in the city.
Authors:O. Baykara, M. İnceöz, M. Doğru, E. Aksoy, and F. Külahcı
On-line monitoring of soil radon (222Rn) concentration system was constructed on one of the main active fault zone of East Anatolian Fault System (EAFS) in Turkey.
The preliminary results, observed during the second part of 2004 and first part of 2005 is presented. During the monitoring
of soil radon concentration, numerous anomalies that equal or twice standard deviation were observed. In addition, the variation
of the radon concentration was examined between the mean values and plus/minus two standard deviations and any increase in
radon concentration above this limit was assumed to be 222Rn anomalies. These anomalies usually appeared between a few days or weeks before the earthquakes occurrence. The obtained
data were also compared as considered respect to the earthquakes occurred in a 100 km radius of the fault system.