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Non renseigné / Most mega-earthquakes (i.e. earthquakes with Mw ≥ 8.5) occur along subduction mega-thrusts, the interfaces between the subducting - and the overriding plates in convergent margins. These events may have catastrophic impact on human societies due to their destructive potential. For this reason being able to predict the timing and size of these earthquakes became one goal of the international scientific community. The subduction seismic cycle is influenced by many different parameters. The interplay between these parameters governing the frequency and size of megathrust earthquakes still remains unclear, mainly due to the short (i.e. limited to the last century) seismic record.The seismogenic part of the subduction thrust fault spans between depths of 11±4 and ± 51 km (Heuret et al. 2011). In this zone a combination of temperature, pressure and rocks characteristics creates conditions favourable for seismic behaviour. Whether a specific area in the subduction thrust fault has the ability to trigger mega-earthquakes can be expressed using the degree of seismic coupling, i.e. the amount of slip that occurs with respect to the total amount of plate convergence (e.g. Scholz 1998; Scholz & Campos 2012). When a fault is fully coupled, all of the fault slip occurs during earthquakes instead of also during aseismic behaviour (e.g. slow slip events). The internal structure of the interplate fault zone mainly determines whether an area within a subduction zone behaves seismic or aseismic (Wang & Bilek 2011). This is influenced by the topography of the plate interface (e.g. subducting seamounts; Wang & Bilek 2014), but also subducted sediments and fluids in the subduction channel may play an important role.The main goal of this project is to understand which parameters affect the behaviour of mega-earthquake ruptures. This will be done by comparing natural data (e.g. seafloor roughness, sediment thickness and fluid content in the subduction channel) to rupture characteristics of major recent earthquakes. With this analysis also more knowledge can be gained on the triggering of slow earthquakes instead of mega-earthquakes. These are slow slip events with lower frequencies and longer durations than ‘regular’ earthquakes (Saffer & Wallace 2015).The database of natural data, implemented by the long-term scientific joint venture between the Univ. Montpellier and the LET (Roma Tre) will be used for the analysis. Ongoing work is done on determining a method for estimating the seafloor roughness, i.e. the distribution of high, low and smooth areas (by Michel Peyret in collaboration with Serge Lallemand, Univ. Montpellier). Also data is available on the trench sediment thickness around the world (Heuret et al. 2011). In the frame of this project, information on the roughness of the seafloor will be added to the database. In addition the rupture characteristics of major recent earthquakes will be collected. By performing a multiparametric statistical analysis of the database, a conceptual model will be realized, exploring the possible link between all the different parameters. The aim is to validate this model in the lab using scaled 3D analogue models. This will be done both at the LET and at Univ. Montpellier by using a broad range of geometries and contact materials with different rheologies (e.g. gelatin, foam rubber and a new analogue material; Caniven et al. 2015; Corbi et al. 2013). This jointed experimental approach with both the Univ. Montpellier and the LET involved creates a rich environment where differences and similarities of the two different approaches can be used to validate the results.

La gran prioridad del ingeniero civil es brindar seguridad al ciudadano en cualquiera de las edificaciones y/o construcciones que este esta seguridad siempre debe estar ligada a obtener la infraestructura adecuada a un costo razonable. En nuestro país los proyectos de construcción, en particular las edificaciones que son nuestro caso en estudio, podrían durante un sismo, presentar diversos motivos de fallas, entre ellos, y en el que nos vamos a enfocar es en la falla producida por el contacto entre estructuras vecinas durante un movimiento sísmico. Consideramos que el rápido aumento de las edificaciones para uso residencial y la todavía existente informalidad en la construcción, han sido algunas de las razones que han generado que en el Perú existan edificaciones contiguas construidas sin una adecuada junta de separación sísmica, a pesar de que en el reglamento de construcción este indicado. Tomando en cuenta que el país se encuentra ubicado en una zona altamente sísmica, dichas edificaciones podrían ser severamente dañadas durante el evento de un movimiento sísmico. Es por tal motivo, que se busca conocer y analizar el efecto en las estructuras adyacentes de concreto armado de juntas de separación sísmicas inferiores a lo reglamentado, determinando la fuerza de impacto producida por el fenómeno de golpeo entre estructuras (pounding). Se considera que la información a obtenerse será de gran importancia, debido a la falta de investigaciones en idioma español en nuestro país sobre dicho fenómeno. Una vez determinada la fuerza de impacto entre las estructuras se esbozarán posibles soluciones que consideremos que podrían ayudar a mitigar el problema. / The main priority for a civil engineer is to provide security to citizens in any buildings and/or constructions he makes, this security always has to be linked to obtain the appropriate infrastructure at reasonable cost. In our country, construction projects specially buildings that are our case of study, could have many causes of failures during an earthquake, among them —and the one we will focus on— is the failure occurred by the contact between neighbor structures during a seismic activity. We consider the rapid increase of buildings for residential use and the yet existing informality in construction have been one of the reasons for generating constructed adjoining buildings without an appropriate seismic separation joints in Peru, in spite of the indications in the building code. Considering that the country is situated in a highly seismically unstable area, these buildings might be severely damaged during a seismic activity. For that reason, we want to discover and analyse the effect in the adjoining reinforced concrete structures of seismic separation joints below regulation, determining the impact force produced by the beating phenomenon between structures (pounding). The information that is going to be obtained is considered to be relevant, due to the lack of researches about this phenomenon in Spanish in our country. Once determined the impact force between structures, possible solutions that we consider might help attenuate the problem will be outlined. / Tesis

A large magnitude, long duration subduction earthquake is impending in the Pacific Northwest, which lies near the Cascadia Subduction Zone (CSZ). Great subduction zone earthquakes are the largest earthquakes in the world and are the sole source zones that can produce earthquakes greater than M8.5. Additionally, the increased duration of a CSZ earthquake may result in more structural damage than expected. Given such seismic hazard, the assessment of reinforced concrete substructures has become crucial in order to prioritize the bridges that may need to be retrofitted and to maintain the highway network operable after a major seismic event. Recent long duration subduction earthquakes occurred in Maule, Chile (Mw 8.8, 2010) and Tohoku, Japan (Mw 9.0, 2011) are a reminder of the importance of studying the effect of subduction ground motions on structural performance. For this purpose, the seismic performance of substandard circular reinforced concrete bridge columns was experimentally evaluated using shake table tests by comparing the column response from crustal and subduction ground motions. Three continuous reinforced columns and three lap-spliced columns were tested using records from 1989 Loma Prieta, 2010 Maule and 2011 Tohoku. The results of the large-scale experiments and numerical studies demonstrated that the increased duration of subduction ground motions affects the displacement capacity and can influence the failure mode of bridge columns. Furthermore, more damage was recorded under the subduction ground motions as compared to similar maximum deformations under the crustal ground motion. The larger number of plastic strain cycles imposed by subduction ground motions influence occurrence of reinforcement bar buckling at lower displacement compared to crustal ground motions. Moreover, based on the experimental and numerical results, subduction zone ground motion effects are considered to have a significant effect on the performance of bridge columns. Therefore, it is recommended to consider the effects of subduction zone earthquakes in the performance assessment of substandard bridges, or when choosing ground motions for nonlinear time-history analysis, especially in regions prone to subduction zone mega earthquakes. Finally, for substandard bridges not yet retrofitted or upgraded seismically, the following performance limit recommendation is proposed: for the damage state of collapse, which is related to the ODOT's Life Safety performance level, the maximum strain in the longitudinal reinforcement should be reduced from 0.09 (in./in.) to a value of 0.032 (in./in.) for locations where subduction zone earthquakes are expected, to take into consideration the occurrence of bar buckling.

Title: Development of effective code for earthquake dynamic source simulations Author: Bc. Jan Premus Department: Department of Geophysics Supervisor: doc. RNDr. František Gallovič, Ph.D, Department of Geophysics Abstract: Dynamic rupture modeling coupled with strong motion data fitting offers an insight into physical mechanisms behind earthquake sources [Gallovic et al., 2019]. Running a large number of dynamic model simulations is required due to the nonlinearity of the inverse problem. The goal of this Thesis is a development of an efficient forward solver for the dynamic inversions. The fi- nite difference staggered grid code FD3D by Madariaga and Olsen [1998] served as a basis for the development, offering sufficient speed, but rather low accu- racy. Traction at split node implementation of the fault boundary condition and perfectly matched layers as the absorbing boundary condition were required to obtain desirable accuracy. In addition to the slip weakening friction law, fast ve- locity weakening friction law has been implemented, increasing the applicability of the code. We test the new code FD3D TSN using USGS/SCEC benchmarks TPV5 (slip-weakening friction) and TPV104 (fast rate weakening friction) [Harris et al., 2018], showing very good agreement with results calculated by advanced numerical...

In the equatorial Pacific Ocean, earthquakes are used as an indicator of tectonic stress for normal faults in the Galapagos Spreading Center, transform faults along the East Pacific Rise and thrust faults in the Middle American subduction zone. Linkages between seafloor tectonic processes and oceanographic and lunar conditions were explored using time-series cross-correlation analyses on two different time scales. Data for earthquakes in the eastern tropical Pacific study area are obtained using the hydrophone arrays of the NOAA-VENTS Program. Hydroacoustic monitoring (listening to underwater sounds) provides scientists with a detailed dataset that includes even small earthquakes, starting as low as magnitude 0.6, that are not perceived by land-based seismographs. Data for sea surface heights (SSH) consist of two different datasets. On a moon's quarter time scale, SSH data used to investigate the influence of the earth tide and changes in oceanic conditions were remotely acquired by the altimeter on board the TOPEX/Poseidon (T/P) satellite. SSH data used to investigate the influence of the ocean tides were obtained from the Tidal Model Driver (Padman and Erofeeva 2003), that predicts SSH for locations every hour. The Geographic Information System (GIS) was used for the visual display of the data and to compute basic descriptive statistics. A lab-book was created for the educational-outreach section of this work, explaining step by step how GIS has been used. Significant results show correlations between normal faults and ocean tides and between the thrust fault and earth tides. Also, the Quebrada and the Discovery transform faults show high correlation of earthquake events, suggesting that at such temporal and spatial resolution, the plate moves as a rigid block. / Graduation date: 2006

Graduation date: 1992

As the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.

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.

The central focus of this dissertation is a seismic vulnerability assessment of retrofitted bridges. The objective of this work is to establish a methodology for the development of system level fragility curves for typical classes of retrofitted bridges using a probabilistic framework. These tools could provide valuable support for risk mitigation efforts in the region by quantifying the impact of retrofit on potential levels of damage over a range of earthquake intensities. The performance evaluation includes the development of high-fidelity three-dimensional nonlinear analytical models of bridges retrofit with a range of retrofit measures, and characterization of the response under seismic loading. Sensitivity analyses were performed to establish an understanding of the appropriate level of uncertainty treatment to model, assess, and propagate sources of uncertainty inherent to a seismic performance evaluation for portfolios of structures. Seismic fragility curves are developed to depict the impact of various retrofit devices on the seismic vulnerability of bridge systems. This work provides the first set of fragility curves for a range of bridge types and retrofit measures. Framework for their use in decision making for identification of viable retrofit measures, performance-based retrofit of bridges, and cost-benefit analyses are illustrated. The fragility curves developed as a part of this research will fill a major gap in existing seismic risk assessment software, and enable decision makers to quantify the benefits of various retrofits.