For a given earth model and hypocenter location, short-period local waveforms are inverted for the six unknown moment tensor rate functions (MTRFs) by a linear procedure. Subsequently, the MTRFs are decomposed into the source time function (STF) and the time independent moment tensor, fully describing the focal mechanism of the event. In case of short epicentral distances, routinely determined hypocenters are usually not accurate enough to be used in focal mechanism inversion. However, introducing hypocenter co-ordinates as unknown parameters leads to a nonlinear inversion problem. In order to solve this nonlinear problem, a probabilistic approach is applied in this study. The a priori probability density function (PDF) for the hypocenter location is given by a routinely used location algorithm. Assuming that all uncertainties can be described by Gaussian PDFs, measurement errors and theoretical errors are estimated. Then the results of the Bayesian approach are the posterior PDFs for both the hypocenter co-ordinates and the MTRFs. Decomposing the MTRFs, the PDFs for the STF and the moment tensor are also deduced. The estimated uncertainties in the moment tensor components are plotted on the focal sphere in such a way, that the significance of the double-couple, the CLVD, and the volumetric parts of the source can be assessed. The method is illustrated through the waveform inversion of a local event that occurred in the central part of the Pannonian Basin. The moment tensor solution for the selected event has negligible volumetric part, implying the tectonic nature of the event. The retrieved mechanism is in agreement with the available clear readings of first-arrival P-wave polarities. The principal axes of the resulting source mechanism also agrees well with the main stress pattern published for the epicentral region.
We determined a new one-dimensional P-wave velocity model for the territory of Hungary based on the first arrival times of local earthquakes. During the computations 910 P-wave arrival data of 86 events from the time period between 1985 and 2010 have been used. The applied methodology is a combination of a genetic algorithm based procedure and an iterative linearized joint inversion technique. The preferred velocity profile has been chosen from the best models based on the data of a series of controlled explosions.The resulting flat-layered model consists of three crustal layers and a half-space representing the uppermost mantle. The crustal compressional velocities vary in the range of 5.3-6.3 km/s, while the uppermost mantle velocity was found to be 7.9 km/s. The Moho is located at an average depth of 26 km.Additionally, the Vp/Vs ratio was calculated by the Wadati-method, which gave a value of 1.74±0.05.
Authors:Z. Wéber, Z. Bus, K. Gribovszki, B. Süle, Gy Szeidovitz, and P. Varga
In this paper, research activities at the Theoretical Division of the Seismology Department of GGRI (in short: Seismological Observatory) are summarized. The reported investigations have been carried out since 1999, when the division was founded with three members. Detailed discussions of the presented results can be found in various national and international scientific journals.
Authors:Szaniszló Z. Jávor, K. Shanava, E. Hocsák, M. Kürthy, J. Lantos, B. Borsiczky, I. Takács, Sz. Horváth, B. Balatonyi, S. Ferencz, A. Ferencz, E. Rőth, and Gy. Wéber
Increased intra-abdominal pressure during laparoscopy leads to hypoxia due to reduced blood flow. Aim of our study was to investigate whether preconditioning can reduce this negative effect of the pneumoperitoneum. Fifty female Wistar rats were used, divided into 5 groups. I: Sham operation (Sham), II: conventional pneumoperitoneum (PP), III: transvaginal pneumoperitoneum (TV), IV: preconditioning for 2.5 minutes in two cycles (Pre 2.5), V: preconditioning for 5 minutes (Pre 5). Malondialdehyde (MDA), reduced glutathione (GSH), sulfhydrylgroup (SH-) concentrations, superoxide-dismutase (SOD) and mieloperoxidase (MPO) activity, and anti-apoptotic pathway marker p-AKT level and inflammatory cytokine TNF-α were measured. SOD activity and GSH concentration were decreased in PP and TV groups comparing to Sham and preconditioning groups. MPO activity was decreased also in PP and TV groups comparing to the Sham group but in the preconditioning groups it has remained high. MDA concentration in plasma was increased in PP and TV groups comparing to Sham and preconditioning groups. There was no difference in the case of blood MDA and SH-concentrations between groups. Anti-apoptotic pathway marker p-AKT level was decreased in the TV group comparing to the sham and preconditioning groups. TNF-α level was increased in TV and preconditioning groups compared to the sham group. According to the results preconditioning can reduce negative effects of pneumoperitoneum.