Correlation-based feature optimization and object-based approach for distinguishing shallow and deep-seated landslides using high resolution airborne laser scanning data

© Published under licence by IOP Publishing Ltd. Landslides post great threats to many regions globally, particularly in densely vegetated areas where they are hard to identify. Thus, in order to address this issue, precise inventory mapping methods are required in order to gauge landslide susceptibility in regions, as well as hazards and risk. Obstacles in the development of such mapping methods, however, are optimization techniques to employ, feature selection methods, as well as the development of model transferability. The present study seeks to utilize correlation-based feature selection and object-based approach in conjunction with LiDAR data, whereby LiDAR-DEM derived digital elevation alongside high-resolution orthophotos are employed in tandem. Next, fuzzy-based segmentation parameter optimizer was employed in order to optimize segmentation parameters. Next, support vector machine was employed in order to assess the effectiveness of the proposed method, with results illustrating the algorithm's robustness with regards to landslide identification. The results of transferability also demonstrated the ease of use for the method, as well as its accuracy and capability to identify landslides as either shallow or deep-seated. To summarize, the study proposes that the developed methods are greatly effective in landslide detection, especially in tropical regions such as in Malaysia

The importance of input data on landslide susceptibility mapping

Landslide detection and susceptibility mapping are crucial in risk management and urban planning. Constant advance in digital elevation models accuracy and availability, the prospect of automatic landslide detection, together with variable processing techniques, stress the need to assess the effect of differences in input data on the landslide susceptibility maps accuracy. The main goal of this study is to evaluate the influence of variations in input data on landslide susceptibility mapping using a logistic regression approach. We produced 32 models that differ in (1) type of landslide inventory (manual or automatic), (2) spatial resolution of the topographic input data, (3) number of landslidecausing factors, and (4) sampling technique. We showed that models based on automatic landslide inventory present comparable overall prediction accuracy as those produced using manually detected features. We also demonstrated that finer resolution of topographic data leads to more accurate and precise susceptibility models. The impact of the number of landslide-causing factors used for calculations appears to be important for lower resolution data. On the other hand, even the lower number of causative agents results in highly accurate susceptibility maps for the high-resolution topographic data. Our results also suggest that sampling from landslide masses is generally more befitting than sampling from the landslide mass center. We conclude that most of the produced landslide susceptibility models, even though variable, present reasonable overall prediction accuracy, suggesting that the most congruous input data and techniques need to be chosen depending on the data quality and purpose of the study

Detecting and Characterizing Active Thrust Fault and Deep-Seated Landslides in Dense Forest Areas of Southern Taiwan Using Airborne LiDAR DEM

Steep topographic reliefs and heavy vegetation severely limit visibility when examining geological structures and surface deformations in the field or when detecting these features with traditional approaches, such as aerial photography and satellite imagery. However, a light detection and ranging (LiDAR)-derived digital elevation model (DEM), which is directly related to the bare ground surface, is successfully employed to map topographic signatures with an appropriate scale and accuracy and facilitates measurements of fine topographic features. This study demonstrates the efficient use of 1-m-resolution LiDAR for tectonic geomorphology in forested areas and to identify a fault, a deep-seated landslide, and the regional cleavage attitude in southern Taiwan. Integrated approaches that use grayscale slope images, openness with a tint color slope visualization, the three-dimensional (3D) perspective of a red relief image map, and a field investigation are employed to identify the aforementioned features. In this study, the previously inferred Meilongshan Fault is confirmed as a NE–SW-trending, eastern dipping thrust with at least a 750 m-wide deformation zone. The site where future paleoseismological studies should be performed has been identified, and someone needs to work further on this site. Signatures of deep-seated landslides, such as double ridges, trenches, main escarpments, and extension cracks, are successfully differentiated in LiDAR DEM images through the use of different visualization techniques. Systematic parallel and continuous lineaments in the images are interpreted as the regional cleavage attitude of cleavage, and a field investigation confirms this interpretation

Detecting and Characterizing Active Thrust Fault and Deep-Seated Landslides in Dense Forest Areas of Southern Taiwan Using Airborne LiDAR DEM

Steep topographic reliefs and heavy vegetation severely limit visibility when examining geological structures and surface deformations in the field or when detecting these features with traditional approaches, such as aerial photography and satellite imagery. However, a light detection and ranging (LiDAR)-derived digital elevation model (DEM), which is directly related to the bare ground surface, is successfully employed to map topographic signatures with an appropriate scale and accuracy and facilitates measurements of fine topographic features. This study demonstrates the efficient use of 1-m-resolution LiDAR for tectonic geomorphology in forested areas and to identify a fault, a deep-seated landslide, and the regional cleavage attitude in southern Taiwan. Integrated approaches that use grayscale slope images, openness with a tint color slope visualization, the three-dimensional (3D) perspective of a red relief image map, and a field investigation are employed to identify the aforementioned features. In this study, the previously inferred Meilongshan Fault is confirmed as a NE–SW-trending, eastern dipping thrust with at least a 750 m-wide deformation zone. The site where future paleoseismological studies should be performed has been identified, and someone needs to work further on this site. Signatures of deep-seated landslides, such as double ridges, trenches, main escarpments, and extension cracks, are successfully differentiated in LiDAR DEM images through the use of different visualization techniques. Systematic parallel and continuous lineaments in the images are interpreted as the regional cleavage attitude of cleavage, and a field investigation confirms this interpretation

Morphology-based landslide monitoring with an unmanned aerial vehicle

PhD ThesisLandslides represent major natural phenomena with often disastrous consequences. Monitoring landslides with time-series surface observations can help mitigate such hazards. Unmanned aerial vehicles (UAVs) employing compact digital cameras, and in conjunction with Structure-from-Motion (SfM) and modern Multi-View Stereo (MVS) image matching approaches, have become commonplace in the geoscience research community. These methods offer a relatively low-cost and flexible solution for many geomorphological applications. The SfM-MVS pipeline has expedited the generation of digital elevation models at high spatio-temporal resolution. Conventionally ground control points (GCPs) are required for co-registration. This task is often expensive and impracticable considering hazardous terrain. This research has developed a strategy for processing UAV visible wavelength imagery that can provide multi-temporal surface morphological information for landslide monitoring, in an attempt to overcome the reliance on GCPs. This morphological-based strategy applies the attribute of curvature in combination with the scale-invariant feature transform algorithm, to generate pseudo GCPs. Openness is applied to extract relatively stable regions whereby pseudo GCPs are selected. Image cross-correlation functions integrated with openness and slope are employed to track landslide motion with subsequent elevation differences and planimetric surface displacements produced. Accuracy assessment evaluates unresolved biases with the aid of benchmark datasets. This approach was tested in the UK, in two sites, first in Sandford with artificial surface change and then in an active landslide at Hollin Hill. In Sandford, the strategy detected a ±0.120 m 3D surface change from three-epoch SfM-MVS products derived from a consumer-grade UAV. For the Hollin Hill landslide six-epoch datasets spanning an eighteen-month duration period were used, providing a ± 0.221 m minimum change. Annual displacement rates of dm-level were estimated with optimal results over winter periods. Levels of accuracy and spatial resolution comparable to previous studies demonstrated the potential of the morphology-based strategy for a time-efficient and cost-effective monitoring at inaccessible areas

Earthquake distributions at volcanoes: models and field observations

Volcanic earthquakes can provide significant insight into physical processes acting at volcanoes, such as magma accumulation and the mechanisms of deformation of the volcanic edifice. At the same time a statistical analyses of volcanic seismicity prior to an eruption (for example variations in the Gutenberg-Richter b-value – a measure of the proportion of large and small events) are a key component of the practical problem of forecasting eruptions. This thesis aims to tackle two key areas of research that are closely related to these important overall goals, by comparing seismic data obtained from currently-active volcanoes with direct field observation of faulting and fracturing from an exhumed extinct volcano. First I introduce a new approach that improves the accuracy and reliability of calculating spatial and temporal variations of the seismic b-value for frequency-magnitude distributions at active volcanoes, and apply it to several test cases. An extensive literature review highlights a large variability and lack of standardisation of methodology used to analyse frequency-magnitude distributions in the past. Motivated by this, I introduce and test a new workflow to standardise calculating completeness magnitudes of seismic catalogues. The review also highlights the fact that uncertainties in estimating the threshold magnitude of complete reporting have been ignored to date. Here I use synthetic catalogues to quantify this previously unidentified source of error, and provide a template to estimate the total error in b-value. In standard analysis it is also common to sample time windows subjectively, although this can introduce bias. Here I develop a new objective, iterative sampling method that calculates the b-value as a full probability density function which need not have a Gaussian error structure. Application of this method reveals ‘mode-switching’ behaviour for the first time in volcanic seismic catalogues. The results also show b-values often do have a value indistinguishable from that of tectonic seismicity (b=1 within error). Nevertheless there are also several robust examples of real high b-values, as high as 3.3. The second part of the study is based on a field campaign to investigate the fracture zones from an exhumed volcanic setting on the Isle of Rum, NW Scotland. Lithological and structural mapping is used to collect structural data that is then used to quantify and explain complex fracture patterns and the underlying intra-magma chamber processes that occurred there in the geological past. In particular I identify a singular collapse event within the youngest volcanic unit, the Central Intrusion. This is responsible for forming the observed igneous breccias and the lineaments on satellite images that I interpret as contemporaneous faults. Using appropriate scaling relations, I infer the b-value for the Rum lineaments data. This would have been relatively high, at a value of approximately 1.9. The final part of the study compares the fracture data on Rum to earthquake distributions at El Hierro volcano, Canary Islands. Here I show the level of fractal clustering is similar in both an extinct (60 Ma) and a currently active volcano. Both show similar high levels of clustering. However, in both cases there is a difference between the capacity and correlation dimensions (D₀≠D₂), implying the set of rupture sources or mapped fault traces form a multi-fractal set. Broadly, the scaling of fracture sets in an ancient volcano has similar properties to those observed in a modern volcano, except that the Rum data imply a greater absolute degree of spatial clustering of deformation than that for the recent unrest at El Hierro

Fallas activas de la cordillera Ibérica Centro-Oriental

Las fallas extensionales recientes de la Cordillera Ibérica centro-oriental limitan o cortan las cuencas neógeno-cuaternarias de Calatayud, Jiloca, Teruel, llegando hasta las fosas del Maestrat. Son las denominadas fallas de Río Grío-Pancrudo, Munébrega, Daroca, Calamocha, Sierra Palomera, Concud, Teruel, Valdecebro, El Pobo, Peralejos-Tortajada-Cabigordo, La Hita y Maestrat. Todas ellas han registrado desplazamientos de escala deca- a hectométrica desde el Plioceno superior, y muchas muestran evidencias de actividad en el Pleistoceno, lo que obliga a tener en cuenta sus correspondientes potenciales sismogénicos. Son el resultado de la inversión negativa de estructuras variscas previas, reactivadas durante la compresión alpina en el Paleógeno y finalmente invertidas en la extensión Neógeno-Cuaternaria. En la actualidad, esta extensión está representada por un campo de esfuerzos radial con una dirección de extensión preferente ENE-WSW. En esta tesis se integra la información disponible en la literatura sobre muchas de estas fallas, que ya habían sido caracterizadas por autores previos, con el estudio en profundidad de las fallas de Río Grío-Pancrudo, Calamocha y Sierra Palomera. Todas ellas han sido investigadas usando métodos estructurales, morfotectónicos y paleosismológicos, y se ha caracterizado su geometría, direcciones de transporte, tasas de deslizamiento y potencial sismogénico. Para el estudio morfotectónico se usa la Superficie de Erosión Fundamental o SEF (3,8¿3,5 Ma) como marcador de la deformación.La falla de Río Grío-Pancrudo es una macroestructura extensional que forma parcialmente el borde noreste de la cuenca de Calatayud, extendiéndose hasta 95 km de longitud, y rehundiendo su relleno mio-plioceno. Su dirección media es NNW-SSE y está dividida en dos segmentos dispuestos en relevo diestro (Río Grío-Lanzuela y Cucalón-Pancrudo). Su actividad extensional ha generado un basculamiento de rollover en su bloque superior, desplazamiento de la SEF, escarpes morfológicos, reversión del drenaje (en el valle del Río Güeimil) y rupturas superficiales en sedimentos del Plioceno superior-Cuaternario. El salto neto máximo de la SEF es de 305-325 m, con una tasa neta a largo plazo de 0,09 mm/a en 3,5 Ma. También produce un salto neto de 155-235 m en los últimos 2 Ma, con una tasa neta de 0,07-0,11 mm/a, y de hasta ca. 22 m en 66 ka, implicando una tasa neta de 0,30-0,36 mm/a. El estudio de una trinchera excavada en el segmento de falla de Cucalón-Pancrudo ha permitido interpretar dos eventos, y un posible tercer evento adicional incierto, comprendidos entre 18 y 3 ka. El salto neto total registrado en la trinchera es de 1,1 m, e implica una tasa neta en este sector de la falla de 0,07-0,08 mm/a para los últimos 18 ka.La falla de Calamocha es una falla normal de 18 km de longitud con dirección NNW-SSE. Desplaza el sector norte de la fosa del Jiloca respecto al sector sur de la cuenca de Calatayud, con un salto neto máximo de la SEF de 190¿230 m y una tasa neta a largo plazo de 0,05¿0,06 mm/a en 3,5 Ma. El estudio paleosismológico evidencia su actividad durante el Pleistoceno superior, con cuatro eventos ocurridos entre 125 y 70 ka, un posible evento anterior a ellos datado en 140 ka y un último evento al que se le asocia una edad de 14 ka. Su tasa neta a corto plazo es de 0,10 mm/a para los últimos 70 ka.La falla de Sierra Palomera también limita la fosa del Jiloca por el este, con dirección NNW-SSE uniforme a lo largo de sus 26 km de longitud. Desplaza la SEF hasta ca. 330, y hasta aprox. 480 m cuando se incluye la componente de bending de su bloque superior, con unas tasas a largo plazo de 0,09-0,10 y 0,13-0,15 mm/a, respectivamente. Una falla antitética a la principal muestra evidencias de actividad durante el Pleistoceno medio-superior, desplazando hasta 2,5 m la superficie de un abanico aluvial. En esa misma falla, una trinchera excavada ha permitido inferir hasta siete eventos, cuya edad no ha podido ser precisada, aunque sí podría acotarse el último evento a una edad de 50 ka. Su análisis retrodeformacional sugiere que los patrones de fracturación han pasado de ser dominantemente sintéticos a antitéticos con la principal, lo que sugiere un cambio de mayor control cinemático de la estructura en rollover a un mayor control dinámico del campo de esfuerzos.Las demás fallas recientes de la Cordillera Ibérica centro-oriental tienen dirección cercana a NW-SE y NNW-SSE, y se encuentran en los márgenes de la cuenca de Calatayud (Munébrega-Gallocanta, Daroca) y la fosa del Jiloca (Concud), así como en la cuenca de Teruel (fallas de la Sierra de El Pobo, Peralejos, Cabigordo, Tortajada, Teruel, La Hita). Con carácter más local, aparecen otras fallas de dirección próxima a E-W (Valdecebro). En el sector oriental de la cadena se extiende el sistema de fosas del Maestrat, de dirección NNE-SSW. Son fallas con longitudes del orden de 10^1 km que desplazan la SEF con saltos máximos del orden de 10^2 m durante el Plioceno superior-Cuaternario, arrojando tasas netas de movimiento a largo plazo de entre 0,05 y 0,15 mm/a (media: 0,08 mm/a; últimos 3,8-3,5 Ma). La mayoría de las fallas también evidencian actividad recurrente durante el Cuaternario. En el sector central, a excepción de las fallas de Daroca y Munébrega-Gallocanta, las tasas a corto plazo (0,05¿0,36 mm/a; media: 0,21 mm/a; Pleistoceno superior) son superiores a las promediadas a largo plazo. Esto contrasta con lo que ocurre en el sector oriental, donde trabajos previos muestran cómo su actividad tiende a disminuir durante el Cuaternario.Integrando esos resultados, se propone un modelo de deformación global de la corteza de la región, en el que el campo de esfuerzos actual es heterogéneo en el espacio y en el tiempo, y refleja la combinación de varios mecanismos geodinámicos que se solapan en la región: (1) la extensión WNW-ESE ligada al rifting en el surco de Valencia, que es dominante en el sector más oriental de la cadena (sobre todo durante el Mio-Plioceno); (2) el proceso de abombamiento o doming cortical que afecta a la Cordillera Ibérica centro-oriental (desde el Plio-Cuaternario), que induce el campo de extensión radial y probablemente intensifica la actividad de las fallas en el sector central (durante el Cuaternario); y (3) la compresión intraplaca NNW-SSE relacionada con el empuje de la Placa Africana, que determina la orientación dominante de las trayectorias de SHmax y SHmin en el sector central de la cadena y favorece la activación de las fallas longitudinales. La propagación del rifting hacia el interior de Iberia y el influjo creciente del doming a lo largo del Plioceno-Cuaternario pueden explicar la aceleración registrada en el movimiento en las fallas principales de Teruel, y su atenuación en las fallas del margen del Surco de Valencia. <br /