In this thesis, a support vector machine (SVM) is used to develop a model to predict Arias Intensity. Arias Intensity is a measure of the strength of ground motions that considers both the amplitude and the duration of ground motions. In this research, a subset of the database from the “Next Generation and the duration of Ground-Motion Attenuation Models” project was used as the training data. The data includes 3525 ground motion records from 175 earthquakes. This research provides the assessment of historical earthquakes using arias intensity data. Support vector machine uses a Kernel function to transform the data into a high dimensional space where relationships between the variables can be efficiently described using simpler models. In this research, after testing several kernel functions, a Gaussian Kernel was selected for the predictive model. The resulting model uses magnitude, epicentral distance, and the shear wave velocity as the predictor of Arias Intensity.

The KiK-net ground motion database is used to develop ground motion prediction equations for Arias Intensity (I_a), 5-95% Significant Duration (Ds_5-95), and 5-75% Significant Duration (Ds_5-75). Relationships are developed both for shallow crustal earthquakes and subduction zone earthquakes (hypocentral depth less than 45 km). The models developed consider site amplification using V_S30 and the depth to a layer with V_S=800 m/s (h₈₀₀). We observe that the site effect for I_α is magnitude dependent. For Ds_5-95 and Ds_5-75, we also observe strong magnitude dependency in distance attenuation. We compare the results with previous GMPEs for Japanese earthquakes and observe that the relationships are similar. The results of this study also allow a comparison between earthquakes in shallow-crustal regions, and subduction regions. This comparison shows that Arias Intensity has similar magnitude and distance scaling between both regions and generally Arias Intensity of shallow crustal motions are higher than subduction motions. On the other hand, the duration of shallow crustal motions are longer than subduction earthquakes except for records with large distance and small magnitude causative earthquakes. Because small shallow crustal events saturate with distance, ground motions with large distances and small magnitudes have shorter duration for shallow crustal events than subduction earthquakes.

Η περιοχή του ανατολικού τμήματος της τάφρου της Κορίνθου αποτελεί μια ταχύτατα αναπτυσσόμενη περιοχή φιλοξενώντας σημαντικότατες υποδομές. Η ανάπτυξη αυτής της περιοχής είναι απειλούμενη από την εξίσου σημαντική σεισμική δραστηριότητα που εμφανίζει και είχε ως αποτέλεσμα, σε προηγούμενους ιστορικούς χρόνους εκτεταμένες καταρρεύσεις κτηρίων, θανάτους ή και την πλήρη καταστροφή πόλεων. Σήμερα, νέες επιστημονικές μέθοδοι επικεντρώνονται στα εντυπωσιακά ρηξιγενή πρανή που τη διατρέχουν, η δράση των οποίων θεωρείται υπεύθυνη για τα ισχυρά σεισμικά επεισόδια που συμβαίνουν στην περιοχή. Η εκτίμηση των γεωμετρικών χαρακτηριστικών των ενεργών ρηγμάτων που εντοπίζονται στο θαλάσσιο και στο χερσαίο νότιο τμήμα της τάφρου οδήγησε σε μορφοκλασματικές κατανομές των δύο πληθυσμών από όπου προέκυψε ότι η κυρίαρχη διαδικασία ανάπτυξης των ρηγμάτων στον Κορινθιακό κόλπο είναι η συνένωση μικρότερων ρηγμάτων. Η διαδικασία αυτή φαίνεται να βρίσκεται σε ένα πιο πρώιμο στάδιο στον θαλάσσιο πληθυσμό, ενώ αντίθετα ο χερσαίος πληθυσμός έχει εισαχθεί σε ένα στάδιο ωριμότητας της παραμόρφωσης. Επιπλέον, διαπιστώθηκε ότι ο διαχωρισμός σε μήκη ρηγμάτων μικρότερα και μεγαλύτερα από 5km αναπαριστά ένα ανώτερο όριο στο οποίο πραγματοποιείται η αλλαγή στον τρόπο ανάπτυξης των ρηγμάτων αλλά μπορεί να συσχετιστεί και με την υποκείμενη μηχανική στρωμάτωση. Από αυτές τις κατανομές επιλέχθηκε μια ομάδα δεκατεσσάρων ρηγμάτων που αποτελούν σαφώς προσδιορισμένες σεισμικές πηγές και κυριαρχούν σε περιοχές με υψηλή σεισμικότητα. Ιδιαίτερα μελετήθηκε το ρήγμα των Κεγχρεών το οποίο είναι παρακείμενο σημαντικών υποδομών και στο οποίο πραγματοποιήθηκε γεωμορφολογική ανάλυση που απέδειξε ότι όλο το ρήγμα είναι ενεργό, αλλά και παλαιοσεισμολογική εκσκαφή στην οποία αναγνωρίστηκαν τρία τουλάχιστον σεισμικά γεγονότα μεγέθους 6.3 με κυμαινόμενη περίοδο επανάληψης. Τέλος, για αυτή την ομάδα ρηγμάτων κατασκευάστηκαν δενδροδιαγράμματα εκτίμησης της σεισμικής επικινδυνότητας από τα οποία υπολογίστηκε η ένταση Arias με τη χρήση διαφορετικής βαρύτητας εμπειρικών σχέσεων. Συνεκτιμώντας τη γωνία κλίσης του πρανούς, την επικρατούσα λιθολογία στην επικεντρική περιοχή καθώς και τα όρια της έντασης Arias εντοπίστηκαν θέσεις που εμφανίζονται επιδεκτικές σε διάφορους τύπους δευτερογενών φαινομένων, όπως ρευστοποιήσεις, ολισθήσεις και πτώσεις βράχων. Οι παράκτιες περιοχές των πόλεων του Κιάτου της Κορίνθου, του Λουτρακίου και οι βόρειες ακτές της χερσονήσου της Περαχώρας φαίνεται να επηρεάζονται σε σημαντικότερο βαθμό από την ενεργοποίηση τέτοιων φαινομένων. / The area of the eastern part of the Gulf of Corinth constitutes a rapid developing region hosting significant infrastructures. The significant seismic activity put a threat on this development as it has been noticed during historical time, triggering extensive collapses, human casualties and total disaster of cities. Today new scientific methods are implemented on the spectacular fault arrays that dissect the graben and whose activity is related to the important seismic events, occurred in the area. The scaling properties estimation of the active faults along the Gulf, both onshore and offshore, defines the fractal distributions of both populations. These fractal distributions show that the main fault growth process is the linkage and interaction between smaller fault segments. The offshore population is characterized by an earlier stage of this process, whereas the onshore population indicates a more mature stage of deformation. Additionally, the subdivision of fault length above and beyond 5km represents a maximum bound, where the change in the growth process takes place, but it can also be associated with the underlying crustal mechanical layering. These fractal distributions determine a selection of a group of fourteen active faults that represent unambiguous seismic sources located on highly seismic areas. From this group, the Kencreai fault was especially studied due to its proximity to essential infrastructure. The geomorphology and palaeoseimological analysis of this fault reveal that the fault is active all along its trace, hosting at least three major seismic events with maximum magnitude 6.3 and fluctuant recurrence interval. Finally, for this fault group, seismic hazard assessment logic trees are produced, that calculate the Arias intensity considering the uncertainty of different attenuation relationships. By evaluating the slope gradient, the lithology conditions in the epicentral area and the upper bounds of the Arias intensity, areas highly susceptible to future site effects such as liquefactions, landslides and rock falls are located. The coastal areas of the Kiato, Corinthos and Loutraki cities and the north coast of the Perachora peninsula as well seem more influenced by site effects induced by major earthquakes.

This thesis addresses two fundamental topics in Engineering Seismology; the application of Probabilistic Seismic Hazard Analysis (PSHA) methodology, and the estimation of measures of Strong Ground Motion. These two topics, while being related, are presented as separate sections. In the first section, state-of-the-art PSHA methodologies are applied to various sites in the Buller Region, South Island, New Zealand. These sites are deemed critical to the maintenance of economic stability in the region. A fault-source based seismicity model is developed for the region that is consistent with the governing tectonic loading, and seismic moment release of the region. In attempting to ensure this consistency the apparent anomaly between the rates of activity dictated by deformation throughout the Quaternary, and rates of activity dictated by observed seismicity is addressed. Individual fault source activity is determined following the application of a Bayesian Inference procedure in which observed earthquake events are attributed to causative faults in the study region. The activity of fault sources, in general, is assumed to be governed by bounded power law behaviour. An exception is made for the Alpine Fault which is modelled as a purely characteristic source. The calculation of rates of exceedance of various ground motion indices is made using a combination of Poissonian and time-dependent earthquake occurrence models. The various ground motion indices for which rates of exceedance are determined include peak ground acceleration, ordinates of 5% damped Spectral Acceleration, and Arias Intensity. The total hazard determined for each of these ground motion measures is decomposed using a four dimensional disaggregation procedure. From this disaggregation procedure, design earthquake scenarios are specified for the sites that are considered. The second part of the thesis is concerned with the estimation of ground motion measures that are more informative than the existing scalar measures that are available for use in New Zealand. Models are developed for the prediction of Fourier Amplitude Spectra (FAS) as well as Arias Intensity for use in the New Zealand environment. The FAS model can be used to generate ground motion time histories for use in structural and geotechnical analyses. Arias Intensity has been shown to be an important strong motion measure due to its positive correlation with damage in short period structures as well as its utility in predicting the onset of liquefaction and landslides. The models are based upon the analysis of a dataset of New Zealand Strong Motion records as well as supplementary near field records from major overseas events. While the two measures of ground motion intensity are strongly related, different methods have been adopted in order to develop the models. As part of the methodology used for the FAS model, Monte Carlo simulation coupled with a simple ray tracing procedure is employed to estimate source spectra from various New Zealand earthquakes and, consequently, a magnitude - corner-frequency relationship is obtained. In general, the parameters of the predictive equations are determined using the most state-of-the-art mixed effects regression procedures.