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Correlation between Radioactive Gases and Tsunami

#1094


System of Monitoring Radioactive Gases Released from the Sea Bottom for Predicting Strong Earthquakes and Tsunami Waves in Coastal Region

Tech Area / Field

  • ENV-SEM/Seismic Monitoring/Environment

Status
3 Approved without Funding

Registration date
15.08.1997

Leading Institute
NIIIT (Pulse Techniques), Russia, Moscow

Supporting institutes

  • Institute of Oceanology, Russia, Moscow\nInstitute of Global Climate and Ecology, Russia, Moscow

Project summary

The monitoring system proposed for development is principally to be used for long-term and continuous observations of changes in radon, thoron and other radionuclide concentrations in the near bottom sea water to establish the correlations of their anomalies with the seismic activity in coastal areas of subduction zones (Kamchatka, Sakhalin, Kuril and Japanese islands, etc.). The majority (up to 90 %) of heavy earthquakes in these regions are known to occur under the sea bottom at distances up to 100 kilometers (on the average) from the coast. Besides quaking the earth surface, the earthquakes can produce catastrophic tsunami waves and are of a great danger to coastal towns, objects of sea production, and the underwater network of oil- and gas pipelines, shipping, etc. The situation demands that technical means be developed for sea seismology and requires reliable short-range (days to months) forecast signs of underwater earthquakes.

One of the effective short-range precursors widely-used presently in geochemical earthquake forecasts is the change in the radon concentration in subsoil gas concentration as well as in natural and well sources of underground water. Relative to the rock of drainage system and well depth radon concentration in these sources can differ as much as 10 to 104 Bq/1. The concentration variations associated with the increased seismology activity in the region can amount to values from several tens to hundreds of percentages depending on the closeness to the epicenter of the expected earthquake and a number of other causes.

The radon concentration level in near the sea surface and oceanic waters is known to be much lower, and depending on the depth, salinity and location, generally changes within 0.003-0.015 Bq/1 against the mean background specific activity 40K of 1.5 Bq/1. Under such low 'radon concentrations and high background, the radon monitoring must be ineffective since a long-term and laborious procedure of releasing radon in a gas form is required, and this is associated with a large relative measurement error.

The estimated measures of radon in samples from the near bottom water were performed by the IORAS associates in the subduction zone of the bay of Avachinsk (the town of Petropavlosk-Kamchatsk). In accordance with forecasts in an area where an earthquake of large magnitude is predicted radon values of about two orders above average were measured. Still higher results (up to 14 Bq/1) are obtained in samples taken from a deep-water device targeted directly at the exit of hydrotherms in the Galapagos spread zone (Dymound et al., 1983). Such radon concentration levels allow us, in principle, to measure the radon volume activity from gamma-radiation of its decay daughter products (e.g., RaB and RaC) directly in sea samples. However, short half-lives of radionuclides under conditions when much time and materials are consumed for taking deep-water samples will limit the monitoring potential.

The purpose of this project is to develop special equipment and techniques providing operative control of radon and other radionuclide concentrations directly in the near bottom sea waters in the zones of subduction and at the exit of hydrotherms. We propose to use the currently available cable and buoy autonomous bottom seismic stations (ABS) widely used in the sea seismology to install the equipment at the bottom, maintain its long-term functioning, as well as to lift it to the surface when needed. This will make it possible to establish a low cost automated monitoring system providing simultaneous seismic observations and general telemetry. The place and time the system will be installed over the fracture zone are statistically assessed beforehand with a help of long-range forecast, in particular, from the intensity and space distribution of epicenters of microearthquakes in the region. The near bottom area of the increased radon level can be localized while in the process of installation of the system by measuring samples from on-board the ship.

To measure radionuclides in the sea water we propose to develop a scintillation gamma-spectrometer of high sensitivity, which can identify most intensive lines in the energy range of 0.3-3 MeV. The system proposed consists of CsI(Tl) crystals with silicon photodiodes which differ favorably from traditional Nal(Tl) with a photoelectron multiplier in smaller overall dimensions, low energy consumption, higher stability, and more effective detection. The original multimodule detector design we propose with a light-diode system of thermo- and autostabilization will, to our mind, provide the required threshold sensitivity (of 0.5 Bq/1 when the measurement does not exceed 30 min) and high energy resolution (not worse than 6% for 60Co). With a detector installed at a distance of 1-2 m from the bottom surface (to provide the protection against the natural gamma-background of bottom sediments) this will account for a practically complete absence of cosmic background such that one can expect maximum accuracy of relative measurements.

Self-emerge buoy stations of the ABS type developed by the IORAS which provide the installation of the equipment at a depth down to 3 km and its self-contained power supply for a period up to a year, can be used as a spectrometer carrier. The spectrometer detector whose dimensions are not larger than Ф 150 ґ 200 mm will be fitted in a separate titanic body with wall thickness not to exceed 5 mm, and will be connected with the help of a hydrojoint with electronic systems and a microprocessor device located inside the station. The available cable communication lines as well as hydroacoustic or radiotranslation channels are supposed to be used for transmitting the information to the coast. This will require a radiobuoy connected with the bottom station through a cable or a hydroacoustic channel.

The realization of the proposed project will provide a technique for deep-water monitoring and a highly sensitive gamma-spectrometer. Further it can be used with ABS to examine forecast signs in a region of heavy earthquakes activity in the bay of Avachinsk! With further slight improvement this spectrometer can also be used to monitor large water bodies in close position to nuclear power plants, radioactive disposal sites at sea, atomic submarine that have sunk, as well as to provide radon monitoring of sources of drinking water, hydrothermal water of active volcanoes and other hydrosources.

The RIPT, IORAS, and IGCE have in their disposal an experimental and productive base, qualified scientific and technical personnel experienced in designing nuclear physics detectors, deep-water seismological stations and monitoring systems needed for the realization of the Project.

The implementation of the above Project agrees with the ISTC objectives aimed at the conversion of military developments, support of the research progress in the field of ecology and attraction of Russian scientists and specialists to the international scientific and technical community.

Role of the Foreign Partners

Within the scientific and technical collaborations with potential foreign partners we suggest that at the first stage of the Project the exchange of information on the Project subject, agreement on technical requirements of the equipment under development with account for the specificity of similar tasks, support in selecting the required equipment and assistance when ordering it be reciprocated. At the second stage, the participation in experiments on processing radon-monitoring techniques, consideration of operation results and joint publications will be established. Further on, if the equipment is in demand, a joint production can be organized.

Presently this project was supported by the Tsunami Project Leader Dr. F.I. Gonzalez (NOAA/PMEL USA), who is interested in its realization. The correspondence with other interested organizations from Japan, Canada and USA is being conducted.

We are interested in establishing scientific and technical contacts and appeal to foreign colleges and scientists to support our Project and to participate in it as foreign partners. We hope that our creative efforts when combined will promote solutions to such important problems as prevention of the negative consequences of earthquakes and tsunamis as well as promoting a number of ecological tasks of radiation monitoring in water environments.


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