foF2 seismo-ionospheric effect analysis: actual data and numerical simulations

Abstract. On the background of seasonal and helio-geomagnetic disturbances, disturbances of the ionization density near noon connected to earthquakes are investigated. The study is performed for some tens of earthquakes with magnitudes M>5 and depths h<70 km, which occur at distances from the vertical sounding stations "Tokyo", "Akita", and "Yamagawa" not larger than R=exp(M)+150 km. The analysis is performed using data registered by the three sounding stations every hour during 30 years. Especially methods of the statistical analysis are applied to search for regularities in the lithospheric-ionospheric links before and after earthquakes. The growth of the mean ionization density N at the F-layer electron density maximum Fof2 five-three days before earthquakes, and the decrease of N approaching the eruption and during a few days after the earthquake is investigated in dependence on both the magnitude of the earthquake M and the ionization density N near the F-layer maximum. It is found that some days before earthquakes the decrease of the ionization density ΔN is proportional to the values of M and N. After the earthquakes, ΔN depends much weaker on the magnitude M, and it is not influenced by the ionization density N. The variations of the ionization density three days before earthquakes do not depend on N and M (within the same order of approximation)

Day-time variations of foF2 connected to strong earthquakes

Abstract. The statistical analysis of the characteristic frequency foF2 of the Earth's ionosphere averaged over mid-day hours – from 11:00 till 17:00 h LT – is carried out. Disturbances of foF2 connected to earthquakes are considered on the background of seasonal, geomagnetic, 11-years and 27-days solar variations. A special normalized parameter F is introduced, which represents the almost seasonal-independent part of foF2. Days with high solar (Wolf number >100) and geomagnetic (∑Kp>30) activity are excluded from the analysis. Events with magnitude M>5, distance from the sounding station R5.5. The obtained phenomenon depends on the magnitude of the earthquake. For events with M>5.5, the reliability of the effect is larger than 95%. For data of more than 80 earthquakes in the vicinity of Petropavlovsk-Kamchatsky and more than 200 earthquakes in the vicinity of Tokyo analogous results are obtained

ОЦЕНКА ВЕЛИЧИН СЕЙСМИЧЕСКИХ ВОЗДЕЙСТВИЙ ПО НАРУШЕНИЯМ И СМЕЩЕНИЯМ В СКАЛЬНЫХ МАССИВАХ

Local rock dislocations and shifts, which occur due to strong seismic impacts, are studied. Natural cases under review include displacements that occurred after strong earthquakes in the 20th century and paleoseismic dislocations revealed by the authors in the crustal rocks in the south-eastern (Russian) part of the Fennoscandia shield. The major goal of the study was to determine parameters of the paleoseismic events in terms of intensity, I, and magnitude, M. Two independent options were used: (1) estimation with reference to similar cases in the instrumental measurements period and to the currently applied scaling systems, and (2) introduction of physical characteristics of disturbances of particular types and habitus and fixed values of displacements of the rock blocks. Numerous local disturbances of the rock massifs with significant rock shifts were systematically reviewed as a set of standard models. Values of mass velocities of seismic impacts (peak ground velocities, PGV), which were needed for initiation of the revealed dislocations, were estimated. In many cases, PGV values were above 1 m/sec, i.e. considerably higher than values conventionally accepted (for ground conditions). For clarifications, data on strong movements and explosions were used, and the whole set of data was found reasonably consistent. It was concluded that the cases with PGV&gt;1 m/sec corresponded to focal areas of earthquakes with M&gt;6 (mainly in the deglaciation period). A graphical chart is proposed for estimation of magnitudes and hypocentral distances of initiating earthquakes in case of maximum PGV within a range from 0.01 to 5.00 m/sec. Based on the graphical chart, parameters are estimated for earthquakes that might have caused the dislocations observed on the main sites of the region under study.В работе рассматриваются локальные нарушения и смещения в скальных породах, возникающие при сильных сейсмических воздействиях. Натурный материал представлен примерами такого рода нарушений при известных сильных землетрясениях XX века, а также древними нарушениями и смещениями на ключевых участках юго-восточной части Фенноскандинавского кристаллического щита (по наблюдениям авторов). Конечная цель состояла в параметризации (в терминах интенсивности, I, и магнитуды, M) палеоземлетрясений по оставленным ими специфическим сейсмонарушениям. Это осуществлялось двумя независимыми путями, а именно, c использованием аналогий других инструментальных наблюдений, а также существующих шкал (1) и путем выведения физических характеристик нарушений определенного типа, габитуса и фиксированных величин смещений скальных блоков (2). Систематизация многочисленных локальных нарушений скальных массивов со значительными смещениями блоков породы представлена в виде ряда типовых моделей. Оценены значения массовых скоростей импульсных воздействий, необходимых для инициирования наблюденных смещений. Во многих случаях они превысили 1 м/с, т.е. оказались существенно больше обычно принимаемых для грунтовых условий. Для объяснения привлечены данные по сильным движениям и по взрывам и показано согласие всего этого комплекса данных. Делается вывод о том, что случаи массовых скоростей &gt;1 м/с соответствуют эпицентральным областям землетрясений с магнитудой M&gt;6 (в основном в период дегляциации). Предложена номограмма для оценки магнитуды и гипоцентрального расстояния инициирующего землетрясения при значениях максимальных массовых скоростей в диапазоне от 0.01 до 5.00 м/с. На основании номограммы оценены параметры землетрясений, которые могли вызвать наблюденные перемещения скальных блоков на ключевых участках региона

Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake (2004, M = 6, California, USA) source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network (from SOPAC Internet archive) and of the availability of the rather detailed aftershock sequence data (http://www.ncedc.org/ncedc/catalog-search.html). The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy/deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop

SEISMIC IMPACT ESTIMATION FROM DATA ON DEFORMATIONS AND DISPLACEMENTS IN ROCK MASSIFS

Local rock dislocations and shifts, which occur due to strong seismic impacts, are studied. Natural cases under review include displacements that occurred after strong earthquakes in the 20th century and paleoseismic dislocations revealed by the authors in the crustal rocks in the south-eastern (Russian) part of the Fennoscandia shield. The major goal of the study was to determine parameters of the paleoseismic events in terms of intensity, I, and magnitude, M. Two independent options were used: (1) estimation with reference to similar cases in the instrumental measurements period and to the currently applied scaling systems, and (2) introduction of physical characteristics of disturbances of particular types and habitus and fixed values of displacements of the rock blocks. Numerous local disturbances of the rock massifs with significant rock shifts were systematically reviewed as a set of standard models. Values of mass velocities of seismic impacts (peak ground velocities, PGV), which were needed for initiation of the revealed dislocations, were estimated. In many cases, PGV values were above 1 m/sec, i.e. considerably higher than values conventionally accepted (for ground conditions). For clarifications, data on strong movements and explosions were used, and the whole set of data was found reasonably consistent. It was concluded that the cases with PGV&gt;1 m/sec corresponded to focal areas of earthquakes with M&gt;6 (mainly in the deglaciation period). A graphical chart is proposed for estimation of magnitudes and hypocentral distances of initiating earthquakes in case of maximum PGV within a range from 0.01 to 5.00 m/sec. Based on the graphical chart, parameters are estimated for earthquakes that might have caused the dislocations observed on the main sites of the region under study

NO-Dependent Mechanisms of p53 Expression and Cell Death in Rat’s Dorsal Root Ganglia after Sciatic-Nerve Transection

Peripheral-nerve injury is a frequent cause of disability. Presently, no clinically effective neuroprotectors have been found. We have studied the NO-dependent expression of p53 in the neurons and glial cells of the dorsal root ganglia (DRG) of a rat’s spinal cord, as well as the role of NO in the death of these cells under the conditions of axonal stress, using sciatic-nerve axotomy as a model. It was found out that axotomy led to the nuclear–cytoplasmic redistribution of p53 in neurons, 24 h after trauma. The NO donor led to a considerable increase in the level of p53 in nuclei and, to a smaller degree, in the cytoplasm of neurons and karyoplasm of glial cells 4 and 24 h after axotomy. Application of a selective inhibitor of inducible NO-synthase (iNOS) provided the opposite effect. Introduction of the NO donor resulted in a significant increase in cell death in the injured ipsilateral DRG, 24 h and 7 days after trauma. The selective inhibitor of iNOS demonstrated a neuroprotective effect. Axotomy was shown to upregulate the iNOS in nuclei and cytoplasm of DRG cells. The NO-dependent expression of p53, which is particularly achieved through iNOS activation, is believed to be a putative signaling mechanism of neural and glial-cell death after axotomy