Multi-hazard risk assessment using GIS in urban areas: a case study for the city of Turrialba, Costa Rica

In the framework of the UNESCO sponsored project on “Capacity Building for Natural Disaster Reduction” a case study was carried out on multi-hazard risk assessment of the city of Turrialba, located in the central part of Costa Rica. The city with a population of 33,000 people is located in an area, which is regularly affected by flooding, landslides and earthquakes. In order to assist the local emergency commission and the municipality, a pilot study was carried out in the development of a GIS –based system for risk assessment and management. The work was made using an orthophoto as basis, on which all buildings, land parcels and roads, within the city and its direct surroundings were digitized, resulting in a digital parcel map, for which a number of hazard and vulnerability attributes were collected in the field. Based on historical information a GIS database was generated, which was used to generate flood depth maps for different return periods. For determining the seismic hazard a modified version of the Radius approach was used and the landslide hazard was determined based on the historical landslide inventory and a number of factor maps, using a statistical approach. The cadastral database of the city was used, in combination with the various hazard maps for different return periods to generate vulnerability maps for the city. In order to determine cost of the elements at risk, differentiation was made between the costs of the constructions and the costs of the contents of the buildings. The cost maps were combined with the vulnerability maps and the hazard maps per hazard type for the different return periods, in order to obtain graphs of probability versus potential damage. The resulting database can be a tool for local authorities to determine the effect of certain mitigation measures, for which a cost-benefit analysis can be carried out. The database also serves as an important tool in the disaster preparedness phase of disaster management at the municipal level

Combining ground penetrating radar and seismic surveys in the assessment of cultural heritage buildings: The study of roofs, columns, and ground of the gothic church Santa Maria del Mar, in Barcelona (Spain)

Combined non-destructive techniques are applied in the study of a historical building in Barcelona. Santa Maria del Mar is a magnificent Mediterranean gothic church built between 1329 and 1383. Two of the most important characteristics of this building are the slender columns and the almost flat rooftop. This structure, used to create a visual impression of a unique space, transmits high loads to the tall columns. Previous to restoration, vaults, roofs, and columns were extensively assessed with non-destructive tests, in order to improve the knowledge of those structures. This information will be used in further simulations to analyse load distributions at each part of the structure. Ground and floor were also studied. The analysis of the columns was based on ground- penetrating radar (GPR) surveys and on seismic tomography. Finally, the dynamic behaviour of the structure was determined by seismic monitoring of the main nave and the bell tower. Results obtained at the radar survey highlight the existence of unexpected anomalies in homogeneous materials, supporting the hypothesis of an inner structure between arches and roof composed by hollow elements. Seismic tomography defined the inner geometry of the columns and detected some damage or lower quality stone in various zones. Seismic monitoring established the perfect junction between the bell tower and the main nave. GPR survey on the floor allowed detecting a large number of graves, and some images suggest the existence of large underground walls and some of the foundations of the main façade.Peer ReviewedPostprint (published version

Seismic vulnerability assessment of the old city centre of Seixal, Portugal

The seismic vulnerability assessment of old traditional masonry building stocks, in a seismic risk mitigation perspective, is truly essential not only for buildings with recognized historical and patrimonial value, but also, in relation to regular buildings. In this sense, this paper approaches the issue of the seismic vulnerability assessment of masonry buildings through the application of a simplified methodology to building stock of the old city centre of Seixal, Portugal. This methodology is based on a vulnerability index, suitable in the evaluation of damage and in the creation of large scale loss scenarios (economical and human). Over 500 buildings were evaluated in accordance with the referred methodology and the results obtained were then integrated into a Geographical Information System tool. The integration of this kind of vulnerability and loss results into a GIS tool allows that city councils or regional authorities make their decisions based on a global view of the site under analysis, which led to more accurate and faster decisions either in terms of risk mitigation strategies or rehabilitation plans. This tool can also assumes great importance in the construction of safety and rescue plans

Ground penetrating radar assessment of historical buildings: the study of the roofs, columns and ground of Santa Maria del Mar, in Barcelona / GPR assessment of the basilica Santa Maria del Mar

Santa Maria del Mar is a magnificent gothic church built between 1329 and 1383 in a neighbourhood outside the city walls, over the remains of a more ancient church. The inhabitants of this district (merchants, downloaders of the port, ship-owners artisans and craftsmen) contributed and took part in the construction of this building. Nowadays it is one of the most representative gothic buildings of Barcelona. The structure was completely studied with GPR in order to obtain useful information for a further restoration. Some of the most interesting results were obtained during the evaluation of the vaults and roofs of the building. Radar images demonstrate that the inner structure was designed in order to diminish the load on the arches and walls. Hollow elements were used to support partly the roof in some areas. Moreover, walls, floors and columns were also assessed, and also the ground outside the building. A large number of graves were located under the church floor, but also some of the radar images suggest the existence of large underground walls. The GPR study of the columns and walls was completed with a seismic survey that demonstrates the existence of zones of non-consolidated materials and defined the joints of the ashlars.Postprint (author's final draft

Site Characterization Using Integrated Imaging Analysis Methods on Satellite Data of the Islamabad, Pakistan, Region

We develop an integrated digital imaging analysis approach to produce a first-approximation site characterization map for Islamabad, Pakistan, based on remote-sensing data. We apply both pixel-based and object-oriented digital imaging analysis methods to characterize detailed (1:50,000) geomorphology and geology from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. We use stereo-correlated relative digital elevation models (rDEMs) derived from ASTER data, as well as spectra in the visible near-infrared (VNIR) to thermal infrared (TIR) domains. The resulting geomorphic units in the study area are classified as mountain (including the Margala Hills and the Khairi Murat Ridge), piedmont, and basin terrain units. The local geologic units are classified as limestone in the Margala Hills and the Khairi Murat Ridge and sandstone rock types for the piedmonts and basins. Shear-wave velocities for these units are assigned in ranges based on established correlations in California. These ranges include Vs30-values to be greater than 500 m/sec for mountain units, 200–600 m/sec for piedmont units, and less than 300 m/sec for basin units. While the resulting map provides the basis for incorporating site response in an assessment of seismic hazard for Islamabad, it also demonstrates the potential use of remote-sensing data for site characterization in regions where only limited conventional mapping has been done

Seismic risk in the city of Al Hoceima (north of Morocco) using the vulnerability index method, applied in Risk-UE project

The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-016-2566-8Al Hoceima is one of the most seismic active regions in north of Morocco. It is demonstrated by the large seismic episodes reported in seismic catalogs and research studies. However, seismic risk is relatively high due to vulnerable buildings that are either old or don’t respect seismic standards. Our aim is to present a study about seismic risk and seismic scenarios for the city of Al Hoceima. The seismic vulnerability of the existing residential buildings was evaluated using the vulnerability index method (Risk-UE). It was chosen to be adapted and applied to the Moroccan constructions for its practicality and simple methodology. A visual inspection of 1102 buildings was carried out to assess the vulnerability factors. As for seismic hazard, it was evaluated in terms of macroseismic intensity for two scenarios (a deterministic and probabilistic scenario). The maps of seismic risk are represented by direct damage on buildings, damage to population and economic cost. According to the results, the main vulnerability index of the city is equal to 0.49 and the seismic risk is estimated as Slight (main damage grade equal to 0.9 for the deterministic scenario and 0.7 for the probabilistic scenario). However, Moderate to heavy damage is expected in areas located in the newer extensions, in both the east and west of the city. Important economic losses and damage to the population are expected in these areas as well. The maps elaborated can be a potential guide to the decision making in the field of seismic risk prevention and mitigation strategies in Al Hoceima.Peer ReviewedPostprint (author's final draft

Shear critical R/C columns under increasing axial load

Structural elements in old reinforced concrete (R/C) frame buildings are often prone to shear or flexure-shear failure, which can eventually lead to loss of axial load capacity of vertical elements and initiate vertical progressive collapse of a building. An experimental investigation of shear and flexure-shear critical R/C elements subjected to increasing axial load is reported herein. The focus is on the effect of vertical load redistribution from axially failing columns on the non-linear (pre- and post-peak) response of neighboring shear-dominated members. The test results along with an analysis of the recorded deformation, strength, stiffness and energy dissipation characteristics shed light on the performance of sub-standard columns under constant and increasing axial load subsequent, or just prior, to failing in shear, thus providing useful insights into the assessment of existing R/C structures