Alejandra Staller

DEVELOPMENT OF A BUILDING EXPOSURE MODEL BASED ON UAV AND 360 IMAGERY FOR SEISMIC RISK ASSESSMENT IN NEJAPA (EL SALVADOR) We develop an exposure and seismic vulnerability database for seismic risk applications in the city centre of Nejapa (El Salvador). This area, as most of the country, is characterised by a very limited availability of open cadastral data, street-level and aerial imagery and LiDAR point clouds.We carry out an on-site campaign integrating aerial street-level images. Aerial images are captured in a drone flight and are used to identify building footprints and roof properties. Façade photos are obtained with a 360º camera during a walk-down survey, provindng information about the number of storeys and wall materials. These data are combined to generate a 3D model of the city centre. Next, buildings are identified, characterised, and assigned a vulnerability and fragility models.This database is used to estimate seismic risk for a simulated Mw 6.7 earthquake on the Guaycume fault near the city. Results show that 71% of buildings would suffer complete damage and 68% of the population would be homeless, with losses exceeding USD 15 million.A dashboard integrating these data are set up to help disseminating the results of the study into stakeholders and decision makers.

We present the progress of the project Twin-ER: Pilot Digital Twin for Earthquake Risk. The goal of the project is the integration of digital models of the city and the Earth into the structure of a digital twin, focused on seismic risk.The Earth model includes the generation of new seismic source models based on maps correlating surface deformation and seismic activity rates. Deformation maps will be determined through the analysis of GNSS time series and InSAR images for several dates. Seismic activity rates will be calculated by combining statistical analyses of the seismic catalog with mechanical analyses of earthquake-related stress changes in the crust. The derived maps will show location-, magnitude-, and time-dependent activity rates. Seismic source models will form the basis for the development of seismic hazard maps and constitute the main component of the Earth model.The city model integrates innovative exposure models based on Cadastral data, enhanced with machine learning and deep learning algorithms to identify building typologies and their seismic vulnerability. These analyses will incorporate data of different nature, such as cadastral reference value or exposure time to high temperatures, with the aim of extending the exposure to a multi-hazard and multi-risk context. The exposure and vulnerability models constitute the main component of the city model.By combining seismic hazard models on one hand, and exposure and vulnerability models on the other, the seismic risk model will be obtained. This model represents the expected damage and losses in a city in the event of an earthquake. Therefore, it is a crucial piece of information for proposing risk mitigation measures and planning emergency response.Both Earth and city models are embebed into the digital twin seismic risk. This digital twin is conceived in a pilot phase. The model will be fed with the results of risk simulations, which can be visualized in a web environment, leaving aspects of data loading automation from updated sensors or external servers and subsequent simulations with that updated data for future developments.The project is applied in two study areas of similar size but different, complementary characteristics. One is southeastern Spain, where (1) seismic activity is moderate, and major earthquakes occur rarely, (2) cities have a relatively old building stock and are more vulnerable to earthquakes, and (3) the availability and accessibility to cadastral data are optimal. The other study area is El Salvador, where (1) there is high seismic activity with frequent large earthquakes, (2) cities have a relatively modern building stock with abundant informal construction, and (3) there is no free access to cadastral data. The advances presented here include the UML model of the entire digital twin, the seismic activity and deformation maps in SE Spain, and the city 3D models of two scenarios of application.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

The El Salvador Fault Zone (ESFZ) accommodates most of the differential motion between the Central America Volcanic Forearc and the Chortís block in Central America. By combining recent Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) observations, we develop the first kinematic block model for El Salvador that jointly inverts both data types. The model refines previous regional studies by resolving slip partitioning within the ESFZ and its continuations in Guatemala and the Gulf of Fonseca. Our preferred model predicts total slip rates of about 14 mm yr⁻¹ across the central ESFZ, distributed between a northern branch (5–8 mm yr⁻¹ dextral, 3–7 mm yr⁻¹ normal) and a southern branch (2–6 mm yr⁻¹ dextral). Dextral motion decreases toward the Jalpatagua Fault in Guatemala and toward the San Miguel Fault in eastern El Salvador, increasing again along the Marrabios Fault in Nicaragua. Subduction coupling beneath El Salvador appears weak (Φ≈0.2) and confined to shallow depths, strengthening westward into Guatemala. These results highlight a strongly coupled volcanic arc and a weakly coupled subduction interface. Future seafloor geodetic measurements and new radar satellite missions could improve constraints on slab coupling and crustal deformation processes in this seismically active region.

In Latin America, high seismic activity drives countries to develop disaster risk reduction policies based on seismic risk studies. This work demonstrates the feasibility of creating a seismic exposure and vulnerability database using remotely sensed data. In Nejapa, El Salvador, a drone flight and 360° photo capture were conducted to generate a 3D model of the city. Buildings were identified, characterised, and assigned a vulnerability model. This database was used to estimate seismic risk for a simulated Mw 6.7 earthquake on the Guaycume fault near the city. Results show that 71% of buildings would suffer complete damage and 68% of the population would be homeless, with losses exceeding USD 15 million. Findings were shared with relevant institutions in El Salvador through a dashboard. The country is currently collecting the same type of data used in the present study to update its cadastre and census. This is an opportunity to replicate this pilot experience in many other cities across the country and to provide open data access, positioning El Salvador at the forefront of civil protection in the Latin American region.