This work deals with two main fields: a) The design, built, installation, test, evaluation, deployment and maintenance of Seismological Network of Crete (SNC) of the Laboratory of Geophysics and Seismology (LGS) at Technological Educational Institute (TEI) at Chania. b) The use of Wavelet Transform (WT) in several applications during the operation of the aforementioned network. SNC began its operation in 2003. It is designed and built in order to provide denser network coverage, real time data transmission to CRC, real time telemetry, use of wired ADSL lines and dedicated private satellite links, real time data processing and estimation of source parameters as well as rapid dissemination of results. All the above are implemented using commercial hardware and software which is modified and where is necessary, author designs and deploy additional software modules. Up to now (July 2008) SNC has recorded 5500 identified events (around 970 more than those reported by national bulletin the same period) and its seismic catalogue is complete for magnitudes over 3.2, instead national catalogue which was complete for magnitudes over 3.7 before the operation of SNC. During its operation, several applications at SNC used WT as a signal processing tool. These applications benefited from the adaptation of WT to non-stationary signals such as the seismic signals. These applications are: HVSR method. WT used to reveal undetectable non-stationarities in order to eliminate errors in site’s fundamental frequency estimation. Denoising. Several wavelet denoising schemes compared with the widely used in seismology band-pass filtering in order to prove the superiority of wavelet denoising and to choose the most appropriate scheme for different signal to noise ratios of seismograms. EEWS. WT used for producing magnitude prediction equations and epicentral estimations from the first 5 secs of P wave arrival. As an alternative analysis tool for detection of significant indicators in temporal patterns of seismicity. Multiresolution wavelet analysis of seismicity used to estimate (in a several years time period) the time where the maximum emitted earthquake energy was observed.

Earthquakes are among the most destructive natural disasters affecting urban populations. Structural damage caused by the earthquakes varies depending not only on the seismic source and propagation properties but also on the soil properties. The amplitude and frequency content of seismic shear waves reaching the earth&rsquo / s surface is dependent on local soil conditions. It is well known that the soft sediments on top of hard bedrock can greatly amplify the ground motion and cause severe structural damage. When the fundamental period of the soil is close to the fundamental period of a structure, structural damage increases significantly. Estimation of the fundamental periods, amplification factors and types of soils is critical in terms of reduction of loss and casualties. For the reasons stated, estimation of dynamic behavior of soils has become one of the major topics of earthquake engineering. Studies for determining dynamic properties of soils depend fundamentally on the estimation of the S-wave velocity profiles, amplification factors and ground response. In this study first, the Multi-Mode Spatial Autocorrelation (MMSPAC) method is used to estimate the S-wave velocity profiles at the sites of interest. This method is different than the other ones in the sense that it works for the higher modes as well as the fundamental mode. In the second part, Horizontal to Vertical Spectral Ratio (HVSR) method will be used on both microtremor and ground motion data. Finally, the amplification factors from alternative methods are compared with each other. Consistent results are obtained in terms of both fundamental frequencies and amplification factors.

This thesis develops and explores two methodologies to assess earthquake ground shaking in southwestern British Columbia based on 1D soil layering and 3D basin structure. To assess site response based on soil layering, microtremor array measurements were conducted at two sites of contrasting geology to estimate Rayleigh-wave dispersion curves. A Bayesian inversion algorithm is developed to invert the dispersion data for the shear-wave velocity (VS) profile together with quantitative uncertainty estimates, accounting rigorously for data error covariance and model parameterization selection. The recovered VS profiles are assessed for reliability by comparison with invasive VS measurements at each site with excellent agreement. Probabilistic site response analysis is conducted based on a sample of VS profiles drawn from the posterior probability density of the microtremor inversion. The quantitative uncertainty analysis shows that the rapid and inexpensive microtremor array method provides sufficient resolution of soil layering for practical characterization of earthquake ground motion. To assess the effects of 3D Georgia basin structure on long-period (> 2 s) ground motion for large scenario earthquakes, numerical 3D finite difference modelling of viscoelastic wave propagation is applied. Both deep (> 40 km) subducting Juan de Fuca plate and crustal (5 km) North America plate earthquakes are simulated in locations congruent with known seismicity. Simulations are calibrated by comparing synthetic waveforms with 36 selected strong- and weak-motion seismograms of the 2001 MW 6.8 Nisqually earthquake. The ratio between predicted peak ground motions in models with and without Georgia basin sediments is applied as a quantitative measure of basin amplification. Steep edges in the upper 1 km of the northwest and southeast extents of the basin are coincident with the appearance of surface waves. Focussing of north-to-northeast propagating surface waves by shallow (< 1 km) basin structure increases ground motion in a localized region of southern Greater Vancouver. This effect occurs for both types of earthquakes located south-southwest of Vancouver at distances greater than ~80 km. The predicted shaking level is increased up to 17 times and the duration of moderate shaking (> 3.4 cm/s) is up to 16 times longer due to the 3D Georgia basin structure. / Graduate