Development of a seismic site-response zonation map for the Netherlands

Earthquake site response is an essential part of seismic hazard assessment, especially in densely populated areas. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on the amplitude of ground shaking. Even though the Netherlands is a low- to moderate-seismicity area, the seismic risk cannot be neglected, in particular, because shallow induced earthquakes occur. The aim of this study is to establish a nationwide site-response zonation by combining 3D lithostratigraphic models and earthquake and ambient vibration recordings. As a first step, we constrain the parameters (velocity contrast and shear-wave velocity) that are indicative of ground motion amplification in the Groningen area. For this, we compare ambient vibration and earthquake recordings using the horizontal-to-vertical spectral ratio (HVSR) method, borehole empirical transfer functions (ETFs), and amplification factors (AFs). This enables us to define an empirical relationship between the amplification measured from earthquakes by using the ETF and AF and the amplification estimated from ambient vibrations by using the HVSR. With this, we show that the HVSR can be used as a first proxy for site response. Subsequently, HVSR curves throughout the Netherlands are estimated. The HVSR amplitude characteristics largely coincide with the in situ lithostratigraphic sequences and the presence of a strong velocity contrast in the near surface. Next, sediment profiles representing the Dutch shallow subsurface are categorised into five classes, where each class represents a level of expected amplification. The mean amplification for each class, and its variability, is quantified using 66 sites with measured earthquake amplification (ETF and AF) and 115 sites with HVSR curves. The site-response (amplification) zonation map for the Netherlands is designed by transforming geological 3D grid cell models into the five classes, and an AF is assigned to most of the classes. This site-response assessment, presented on a nationwide scale, is important for a first identification of regions with increased seismic hazard potential, for example at locations with mining or geothermal energy activities.

Development of a country-wide seismic site-response zonation map for the Netherlands

Earthquake site-response is an essential part of seismic hazard assessment, especially in densely populated areas. The shallow geology of the Netherlands consists of a very heterogeneous soft sediment cover, which has a strong effect on seismic wave propagation and in particular on the amplitude of ground shaking, resulting in significant damage on structures despite the fact that the events are of small magnitude. Even though it is a low-to-moderate seismicity area, the seismic risk cannot be neglected, in particular, because shallow induced earthquakes occur. The aim of this study is to establish a nationwide site-response zonation by using the lithostratigraphy, earthquake- and ambient vibration recordings. In the first step, we constrain the parameters (velocity contrast and shear-wave velocity) that are indicative of ground-motion amplification in the Groningen area. For this, we combine ambient vibration and earthquake recordings using resp. the horizontal-to-vertical spectral ratio method (HVSR), borehole empirical transfer functions (ETFs) and amplification factors (AFs). This enables us to define an empirical relationship between measured earthquake amplification from the ETF and AF, and amplification estimated with the HVSR derived from the ambient seismic field. Therewith, we show that the HVSR can be used as a first proxy for amplification. Subsequently, HVSR curves throughout the Netherlands are estimated. The resulting peak amplitudes largely coincide with the in-situ lithostratigraphic sequences and the presence of a strong velocity contrast in the near-surface. Next, sediment profiles representing the Dutch shallow subsurface are categorized into five classes, where each class is representing a level of expected amplification. The mean amplification for each class, and its variability, is quantified using 66 sites with measured earthquake amplification (ETF and AF) and 115 sites with HVSR curves. The site-response (amplification) zonation map for the Netherlands is designed by transforming published geological 3D grid cell models into the five classes and an AF is assigned to most of the classes. This presented site-response assessment on a national scale is important for a first identification of regions with increased seismic hazard potential, for example at locations with mining or geothermal energy activities.

GIS-Based Study To Develop Landslide Susceptibility Zonation Map Of District Mandi, Himachal Pradesh

Rising Incidents of landslide at district Mandi is issue of concern in Himachal Pradesh. Every year many people losses their life and property in these landslide event. This study is conducted with aim to preparation of landslide susceptibility zonation map of district Mandi using method of frequency ratio. Causative factor of landslide involved in preparation of Landslide susceptibility zonation map is Lithology, Slope, Drainage density, Aspect and Land use land cover. Slope, Drainage density, Aspect map are extracted through digital elevation model. Source of Digital elevation model used here is based on SRTM data whereas lithology map is based on data of geological survey of India. Land use land cover map is extracted by images of Landsat 8 satellite. Total of 52 existing landslides are used to model final map. LSZ map show 40.42% area is falling under medium susceptibility class, 34.5 % under low and 25.07% is under high susceptibility class which cover tehsils Mandi, Chachyot, Thunag and some part of Padhar, Aut and Bali Chowki. Further to validate these result areas under curve (AUC) method is use which give prediction rate of 76.06%.

Landslide Hazard Zonation and Evaluation Around Debre Markos Town, NW Ethiopia—A GIS-Based Statistical Approach

The main goal of this research was to perform a landslide hazard zonation and evaluation around Debre Markos town, North West Ethiopia, found about 300 km from the capital city Addis Ababa. To achieve the aim, a GIS-based probabilistic statistical technique was used to rate the governing factors, followed by geoprocessing in the GIS setting to produce the landslide hazard zonation map. In this research, eight internal causative and external triggering factors were selected: slope material (lithology and soil mass), elevation, aspect, slope, land use land cover, curvature, distance to fault, and distance to drainage. Data were collected from field mapping, secondary maps, and digital elevation models. Systematic and detailed fieldwork had been done for image interpretation and inventory mapping. Accordingly, the past landslides map of the research area was prepared. All influencing factors were statistically analyzed to determine their relationship to previous landslides. The results revealed that 17.15% (40.60 km2), 25.53% (60.45 km2), 28.04% (66.39 km2), 18.93% (44.83 km2), and 10.36% (24.54 km2) of the research area falls under no hazard, low hazard, moderate hazard, high hazard, and very high hazard respectively. The validation of the landslide hazard zonation map reveals that 1%, 2%, 3%, and 94% of past landslides fall in no hazard zone, low hazard, moderate hazard zone, and high hazard or very high hazard zones respectively. The validation of the landslide hazard zonation map thus, it has been adequately demonstrated that the adopted approach has produced acceptable results. The defined hazard zones can practically be utilized for land management and infrastructure construction in the study area.

Slope Mass Rating-based Analysis to Assess Rockfall Hazard on Yogyakarta Southern Mountain, Indonesia

In the Parangtritis Beach tourism area located in the Southern Mountain of Yogyakarta, karst hills were excavated to build the main accessing road and produce some of long and very steep slopes along the sides of the road. But still, there was none of the slope reinforcement installed along the road. Meanwhile, at several nearby locations within Southern Mountain, rockfall incidents have occurred many times even caused casualties. The potential of rockfall hazard also could be found in the main road of Parangtritis Beach as the study area. The purpose of this study is to determine the rockfall hazard assessment along the main road using Slope Mass Rating (SMR) analysis with the additional parameter of the slope height and the rock block size. The necessary data obtained by direct measurement and laboratory test. Geomechanics analysis, stereographic projection analysis, and hazard parameters weighting were carried out to produce the Rockfall Hazard Zonation Map of the study area. Based on 17 measurement stations, there are 4 (four) rockfall hazard classes in the study area, i.e., very low, low, moderate, and high. The class of very low, which also included road segments without slope, has the largest percentages of 83.83%, followed by the classes of moderate, low, and high with the percentage of 7.16%, 4.28%, and 4,19%, respectively. SMR was assumed as the most significant parameter that influences the rockfall hazard zonation. Historical rockfall points were overlaid over the Rockfall Hazard Zonation Map to validate the predicted hazard zones. Since 91.23% of the rockfall occurred in the moderate and high hazard classes, the zonation map considered reliable to predict future rockfall. This study also identified several landslide potential zones and provides the recommendation of slope reinforcement to be installed in the study area. Keywords: Rockfall, Slope Mass Rating, Hazard zonation, Slope reinforcement, Hills.

Slope Mass Rating-based Analysis to Assess Rockfall Hazard on Yogyakarta Southern Mountain, Indonesia

In the Parangtritis Beach tourism area located in the Southern Mountain of Yogyakarta, karst hills were excavated to build the main accessing road and produce some of long and very steep slopes along the sides of the road. But still, there was none of the slope reinforcement installed along the road. Meanwhile, at several nearby locations within Southern Mountain, rockfall incidents have occurred many times even caused casualties. The potential of rockfall hazard could also occur in the main road of Parangtritis Beach as the study area. The purpose of this study is to determine the rockfall hazard assessment along the main road using Slope Mass Rating (SMR) analysis with the additional parameter of the slope height and the rock block size. The necessary data obtained by direct measurement and laboratory test. Geomechanics analysis, stereographic projection analysis, and hazard parameters weighting were carried out to produce the Rockfall Hazard Zonation Map of the study area. Based on 17 measurement stations, there are 4 (four) rockfall hazard classes in the study area, i.e. very low, low, intermediate, and high. The very low class, which also included road segments without slope, has the largest percentage of 83.83%, followed by the classes of intermediate, low, and high with the percentage of 7.16%, 4.28%, and 4,19%, respectively. SMR was assumed as the most significant parameter that influences the rockfall hazard zonation. To validate the predicted hazard zones, historical rockfall points were overlaid over the Rockfall Hazard Zonation Map. Since 91.23% of the rockfall occurred in the intermediate and high hazard classes, the zonation can be considered reliable to predict future rockfall. This study also identified several landslide potential zones and provides the recommendation of slope reinforcement to be installed in the study area.

Slope Mass Rating-based Analysis to Assess Rockfall Hazard on Yogyakarta Southern Mountain, Indonesia

The main road to the Parangtritis Beach tourism site in the southern Yogyakarta Province, Indonesia, has full of local and economic activities. The road was made mainly by karst mountains cutting and resulting in almost vertical long and high slopes by its side. Rockfall is being the most potential hazards occurred in this area. The purpose of this study is to determine the rockfalls hazard assessment along the main road using Slope Mass Rating (SMR) analysis. Parameters used in rockfall hazard assessment are SMR with additional valuation from the slope height and the block size. The necessary data of each parameter obtained by direct measurement and the uniaxial compressive strength test in the laboratory. Geomechanics analysis, stereographic projection analysis, and hazard parameters weighting are needed to produce research results in form Rockfall Hazard Zonation Map in the research location. The results showed that the largest percentage of rockfalls hazard class is very low class, with 83,83% of the total hazard classes, associated with normal SMR score (51,66 – 51,75), slope height between 2,85 – 4,57 m, and block size 0,2 – 0,3 m. Followed by intermediate class with 7,16% of the total hazard classes with very bad to bad SMR score (5,82 – 38,15), slope height between 4,26 – 8,96 m, and block size 0,3 – 1,0 m. In the third position followed by a low class with 4,28% of the total hazard classes with bad to normal SMR score (31,17 – 53,03), slope height between 3,52 – 5,28 m, and block size 0,2 – 0,7 m. The last position was taken by high class with 4,19% of the total hazard classes with very bad to bad SMR score (18,31 – 36,50), slope height between 3,62 – 7,82 m, and block size 0,7 – 1,3 m. The SMR analysis also identified the influence of rock types with the rockfall occurrence. Hazard zonation map verification showed a congeniality with the results of rockfalls quantity inventory in the research area.

Factors controlling building damage distribution of the November 26 Mw 6.4 Albania earthquake

<p>On November 26, 2019, an earthquake struck the central western part of Albania. It was assessed as Mw 6.4. Its epicenter was located offshore northwestern Durrës, in a distance of about 7 km north of the city and 30 km west from the capital city of Tirana. Its focal depth was about 10 km. Based on the focal plane solutions provided by several seismological institutes and observations, the mainshock was generated by the activation of a NW-SE striking reverse fault. Unfortunately, the earthquake claimed the lives of 52 people. Few hours after the mainshock, the authors visited the earthquake affected areas in order to conduct a field macroseismic survey and geological reconnaissance for assessing the earthquake impact on the building stock. The dominant buildings in the affected area are buildings with load bearing solid brick walls and concrete floor slabs, precast concrete panel buildings and buildings with reinforced concrete (R/C) frame and infill and partition walls. The main characteristic in the majority of these structures is the presence of prefabricated concrete floor slabs with width of 0.7-1.0 m and no connections between them. Building damage was distributed along two ellipses, whose major axis is oriented generally NW-SE. The western ellipse of major damage was observed in Durrës city, located within the Periadriatic Depression, and the eastern one in Thumanë, Laç, Fushë-Krujë, Kamëz towns and Tirana city along the eastern margin of the Tirana Depression. This NW-SE orientation coincides with the strike of the seismogenic fault as it is derived from the fault plane solutions. The first building type presents slight non-structural and structural damage in Durrës city. However, buildings of this type in Thumanë suffered very heavy structural damage including partial collapse resulting in many fatalities. The second type did not suffer significant non-structural or structural damage. The majority of the observed R/C multistorey buildings in Durrës suffered damage to the lower three to four storeys, while the above storeys remained intact. Damage is attributed to the soft soils in the earthquake-affected areas, the undesired resonance phenomena in high buildings, the large duration of the earthquake shaking, the shallow water table in coastal and swamp areas, the pre-existing stress of buildings founded on soft soils characterized by differential settlements and possible liquefaction phenomena, the poor construction quality and workmanship of the affected buildings, the interventions made, the ageing of materials due to differential displacements of the foundation soil, the applicable antiseismic regulations of the time, if ever were applied, the lack of maintenance and inadequate repair after previous destructive earthquakes and the impact of the September 21, 2019 Mw 5.6 earthquake on the buildings of the affected area. The damage are considered typical of an earthquake of this magnitude. The effect of the previous September 21, 2019 Mw 5.6 earthquake in the same area should be also taken into account. Based on the seismic zonation map of Albania, it is concluded that the resulted intensities from the 2019 earthquake are within the limits specified in the Seismic Zonation Map.</p>