On February 6, 2023, two major earthquakes with magnitudes Mw = 7.7 and Mw = 7.6 struck southeastern Turkiye, causing catastrophic damage and loss of life across 11 provinces, including Malatya. This study focuses on documenting the geotechnical observations and structural damage in Dogansehir, one of the hardest-hit districts not only in Malatya but in the entire affected region. An overview of the-region's tectonic and geological background is presented, followed by an analysis of ground motion data specific to Malatya. A detailed examination of seismic data from stations near Dogansehir was provided to better understand the seismic demands during the earthquakes. The paper then provides insights into the geotechnical conditions, building characteristics, and a damage ratio map of Dogansehir. The influence of local tectonics and geology on the observed damage is analyzed, alongside an evaluation of the seismic performance of masonry and reinforced concrete structures. Dogansehir, located near the epicenters of the Kahramanmaras earthquakes, suffered major structural damage. This was due to the surface rupture occurring near the settlement areas, the establishment of the district centre on the alluvial soil layer and the deficiencies/errors in the building systems. Building settlements on or near active fault zones, as well as on soft soil, leads to serious consequences and should be avoided or require special precautions.

To ensure the seismic safety of important buildings and infrastructure facilities in seismically active areas, it is necessary that, in addition to the various ground motion parameters, the seismic hazard is also characterized in terms of many other destructive natural effects of earthquakes like soil liquefaction and permanent fault displacement for example. The probabilistic seismic hazard analysis methodology can in principle be applied to quantify any of the destructive effects of the earthquakes in a region, provided a formulation has been developed to compute the probability with which a specified level of that effect can be exceeded at a site of interest due to given earthquake magnitude and location. Several investigators have developed necessary relationships and methodologies to estimate this probability for the permanent fault displacement, which may be a potential and primary cause of damage to long structures like bridges, tunnels, pipelines, dams and buried structures, if an active fault happens to cross or pass by such a structure. Based on a comprehensive literature survey and critical analysis of the results obtained for various possible alternatives, we have finalized a methodology for probabilistic fault displacement hazard analysis suitable for a 257 km long strand of the main boundary thrust (MBT) in the Garhwal-Kumaon Himalaya. Formulations are proposed for estimation of both the on-fault principal displacement and the off-fault distributed displacement, which can also be applied to any other thrust fault in any other segment of the Himalaya. The application of the proposed methodology to obtain the on-fault displacement estimates for a site at the midpoint of the selected strand of the MBT is found to provide physically realistic displacement values for very long return periods of upto 100,000 years. The off-fault displacements are found to decrease very fast with distance from the site on MBT and become practically insignificant at a distance of only two km.

On 15 January 2023, a shallow, moderate earthquake with a magnitude (Mw) of 4.7 and a depth of one kilometer struck the northern part of Leyte Island in the central Philippines. Originating along the northern Leyte segment of the Philippine Fault, a well-established creeping fault, the earthquake caused significant geologic, structural, and socio-economic impacts despite its low magnitude. Probable surface rupture and landslides were reported, leading to a comprehensive field investigation. Our investigation revealed an similar to 8 km discontinuous surface rupture along the northern Leyte segment of the Philippine Fault, with a maximum left-lateral displacement of 2 cm. This was the first documented occurrence of such a phenomenon associated with an earthquake of a magnitude less than 6, particularly along a creeping fault segment. The maximum ground shaking felt was reported on the PHIVOLCS Earthquake Intensity Scale (PEIS) to be VI (very strong), equivalent to a Modified Mercalli Intensity (MMI) of VI along the fault strike. However, strong motion accelerographs recorded a peak ground acceleration (PGA) of 0.407 g, equivalent to PEIS VIII (very destructive), attributed to local site amplification influenced by subsurface geology. In the area where the local site amplification occurred, limited liquefaction was observed on marshlands with recent and alluvial deposits. Two landslides were observed in the mountainous area west of the fault. Structural damages were noted in areas with PEIS VI intensity and areas transected by the surface rupture. Despite the earthquake's low magnitude, the event documented significant impacts, including surface ruptures, liquefaction, landslides, and severe structural damage. The peculiarities of this event are attributed to the shallowness of the earthquake source, and local site conditions, including geology, geomorphology, and soil properties, contributed to the severity of the impacts. Moderate in size, this earthquake emphasizes the importance of documenting moderate-sized earthquakes as a tool and guide for medium- and long-term earthquake risk assessment and resiliency.

Performance-based seismic design methods for bridges are advancing, yet limited research has explored the damage mechanisms of bridges subjected to extreme seismic effects, such as those near or across faults. To investigate the damage mechanisms under bedrock dislocation and bridge rupture resistance, providing essential insights for the standardized design and construction of bridges in close proximity to seismic rupture sites, we developed a large-scale device to model bridges in the immediate vicinity of tilted-slip strong seismic rupture sites. This included a synchronous bedrock dislocation loading system. Four sets of typical sandy soil modeling tests were concurrently conducted. The results indicate: (1) The overall shear deformation zone of the foundation and surface uneven deformation primarily concentrate the overburdened soil body along the fault dip. The damaged area under the low-dip reverse fault is lighter on the surface and inside the soil body compared to the high-dip-positive fault. (2) The presence of bridges reduces the width of the main rupture zone and avoidance distance to some extent. However, this reduction is not as significant as anticipated. The damage to the bridge pile foundation along the fault dislocation tendency notably leads to the bending damage of the bridge deck. (3) Input parameters for fracture-resistant bridge design (surface rupture zone location, extent, maximum deformation, etc.) can be deduced from the free site. Within the rupture zone, a fuse design can be implemented using simply supported girders. Additionally, combining the fuse design with simple supported girders on both sides and utilizing simple support beams for fuse design within the rupture zone, along with structural disconnection, allows for reinforcing measures on the bridge structure's foundation platform and pile in the soil body.