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941.
中国大陆科学钻探主孔0-2000米流体地球化学异常与地震的关系 总被引:3,自引:1,他引:3
CCSD流体中He、N2、Ar是记录地震的敏感载体,可能记录了本地一些中小地震及远强震的异常信息。与远强震对应的流体异常幅度大,一般始于远强震前数天,且He、He/Ar、N2/Ar多为负异常,Ar多为正异常;而本地中小地震大多造成主孔流体组分的小幅度波动变化。远强震可能改变了CCSD钻探区的地下流体循环,地震期间监测到泥浆中相对富Ar贫N2和He的地下流体贡献增加,震后,地震引起的附加流体贡献逐渐消失。CCSD的流体组分和比值可能记录了区内地壳应力变化,反映了远强震期间区域构造活动乃至地球深部构造活动产生的场兆、源兆信息,地壳屈曲的假设可以加深CCSD流体作为远强震敏感载体的理解。远强震期间CCSD流体异常也可能是记录了震前长周期波传播至CCSD主孔时激发的流体变化,反映了震源区的应力变化。 相似文献
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We present an inversion technique based on the Marquardt algorithm to estimate the depth of a 2.5-D sedimentary basin in addition
to the regional gravity anomaly that is associated with the residual gravity anomaly, wherein the density contrast varies
parabolically with depth. Forward modeling is carried out through a derived analytical gravity expression of a 2.5-D vertical
prism. Inversion of a theoretical gravity anomaly with and without a regional gravity anomaly illustrates the procedure that
it is found to be insensitive to the regional gravity effect. Furthermore, the algorithm is exemplified with the gravity anomalies
of the derived density-depth model of the Godavari subbasin, India with a parabolic density profile resulting in a more consistent
geological model rather than a constant density profile. The main advantage of this method is that it works well even when
the profile of interpretation does not bisect the strike length of the sedimentary basin. 相似文献
945.
Jean-Paul Toutain Margot Munoz Jean-Louis Pinaud Stéphanie Levet Matthieu Sylvander Alexis Rigo Jocelyne Escalier 《Pure and Applied Geophysics》2006,163(4):723-744
Groundwater coseismic transient anomalies are evidenced and characterized by modelling the mixing function F characteristic
of the groundwater dynamics in the Ogeu (western French Pyrénées) seismic context. Investigations of water-rock interactions
at Ogeu indicate that these mineral waters from sedimentary environments result from the mixing of deep waters with evaporitic
signature with surficial karstic waters. A 3-year hydrochemical monitoring of Ogeu springwater evidences that using arbitrary
thresholds constituted by the mean ± 1 or 2σ, as often performed in such studies, is not a suitable approach to characterize transient anomalies. Instead, we have used
a mixing function F calculated with chemical elements, which display a conservative behavior not controlled by the precipitation of a mineral
phase. F is processed with seismic energy release (Es) and effective rainfalls (R). Linear impulse responses of F to Es and R have been calculated. Rapid responses (10 days) to rainwater inputs are evidenced, consisting in the recharge of the shallow
karstic reservoir by fresh water. Complex impulse response of F to microseismic activity is also evidenced. It consists in a 2-phase hydrologic signal, with an inflow of saline water in
the shallow reservoir with a response delay of 10 days, followed by an inflow of karstic water with a response delay of 70
days, the amount being higher than the saline inflow. Such a process probably results from changes in volumetric strain with
subsequent microfracturation transient episodes allowing short inflow of deep salted water in the aquifer. This study demonstrates
that groundwater systems in such environments are unstable systems that are highly sensitive to both rainfall inputs and microseismic
activity. Impulse responses calculation of F to Es is shown to be a powerful tool to identify transient anomalies. Similar processing is suggested to be potentially efficient
to detect precursors of earthquakes when long time-series (5 years at least) are available in areas with high seismicity. 相似文献
946.
GPS observations of the European permanent network were used to identify seismo-ionospheric precursors of Baltic Sea earthquake
of 21 September 2004. It is a very rare event for this region of Europe (magnitude of about 5.0). This value is the threshold
for the occurrence of seismic effects in the ionosphere. In total electron content (TEC) data over the region of the earthquake,
a specific ionospheric anomaly appeared one day before the earthquake was detected. The ionospheric variability had a positive
sign with an enhancement of about 4–5 TECU (1 TECU = 1016 electrons/m2) relative to the non-disturbed state of the ionosphere. The anomaly had a duration of 4–5 hours in the day time. The special
size of this anomaly was about 1000 km. The characteristic parameters of the anomaly show that it can be associated with ionospheric
precursors of an earthquake. 相似文献
947.
In this study the geodynamical scenario along with concepts of mantle plume and mobile belts is utilized to show that most of the existing and potential high thermal regions fall along the (mobile arms affected by the outburst and) traces of mantle plumes. Effects of channeling and partitioning of thermomagmatic flux (TMF) due to these mantle plumes along the mobile belts, particularly near the triple junctions, can be seen in the form of high heat flow and presence of hot springs. Triple junctions manifest over the Indian lithosphere are: Kutch-Cambay, Narmada Son-Godavari, Tapi-Mahanadi, Tapi-Damodar, Pondicherry region, Gulf of Mannar and SW corner of the subcontinent (off-shore), etc. Apart from mobile belts, the deltaic regions of Krishna, Godavari, Ganga, Cauvery, Narmada-Tapi and Indus, etc., are also posses higher level of thermal anomalies as these regions seem to have been substantially influenced by outbursts and traces of Reunion, Kerguelen, Marion and Crozet hotspots. This is reflected from the correlation between plume affected mobile belts and high heat flow regions, large number of hot springs, anomalous electrical conductivity and also deformation or seismicity. Such correlation can be seen along Cambay, west coast trend, Narmada-Son lineament zone, Godavari-Damodar grabens and Bengal basin. Himalayan belt being ongoing collision zone, thermal anomalies are identified in the form of hot springs along the Himalayan arc. At some locations, which might be junction of tectonic trends, there exist significantly large thermal outputs. Puga in Himalayan region is one such example, as seen from high heat flow (max. 468 mW m− 2) and geothermal gradient (234 °C/km max.). Similarly, Tatapani in Narmada Son Lineament (NSL) region is another such example. The present study discusses the correlation between thermal reservoirs identified by magnetotelluric (MT) study results and plume activity and suggests the need for systematic and detailed MT investigations along plume activated mobile strips in other regions to search for geodynamical history and geothermal resources. 相似文献
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Ginette Saracco Frédérique Moreau Pierre-Etienne Mathé Daniel Hermitte Jean-Marie Michel 《Geophysical Journal International》2007,171(1):87-103
We have previously developed a method for characterizing and localizing 'homogeneous' buried sources, from the measure of potential anomalies at a fixed height above ground (magnetic, electric and gravity). This method is based on potential theory and uses the properties of the Poisson kernel (real by definition) and the continuous wavelet theory. Here, we relax the assumption on sources and introduce a method that we call the 'multiscale tomography'. Our approach is based on the harmonic extension of the observed magnetic field to produce a complex source by use of a complex Poisson kernel solution of the Laplace equation for complex potential field. A phase and modulus are defined. We show that the phase provides additional information on the total magnetic inclination and the structure of sources, while the modulus allows us to characterize its spatial location, depth and 'effective degree'. This method is compared to the 'complex dipolar tomography', extension of the Patella method that we previously developed. We applied both methods and a classical electrical resistivity tomography to detect and localize buried archaeological structures like antique ovens from magnetic measurements on the Fox-Amphoux site (France). The estimates are then compared with the results of excavations. 相似文献