Semiautomatic algorithm to map tectonic faults and measure scarp height from topography applied to the Volcanic Tablelands and the Hurricane fault, western US

Observations of fault geometry and cumulative slip distribution serve as critical constraints on fault behavior over temporal scales ranging from a single earthquake to a fault's complete history. The increasing availability of high-resolution topography (at least one observation per square meter) from air and spaceborne platforms facilitates measuring geometric properties along faults over a range of spatial scales. However, manually mapping faults and measuring slip or scarp height is time-intensive, limiting the use of rich topography datasets. To substantially decrease the time required to analyze fault systems, we developed a novel approach for systematically mapping dip-slip faults and measuring scarp height. Our MATLAB algorithm detects fault scarps from topography by identifying regions of steep relief given length and slope parameters calibrated from a manually drawn fault map. We applied our algorithm to well-preserved normal faults in the Volcanic Tablelands of eastern California using four datasets: (1) structure-from-motion topography from a small uncrewed aerial system (sUAS; 20 cm resolution), (2) airborne laser scanning (25 cm), (3) Pleiades stereosatellite imagery (50 cm), and SRTM (30 m) topography. The algorithm and manually mapped fault trace architectures are consistent for primary faults, although can differ for secondary faults. On average, the scarp height profiles are asymmetric, suggesting fault lateral propagation and along-strike variations in the fault's mechanical properties. We applied our algorithm to Arizona and Utah with a specific focus on the normal Hurricane fault where the algorithm mapped faults and other prominent topographic features well. This analysis demonstrates that the algorithm can be applied in a variety of geomorphic and tectonic settings.Peer reviewedGeolog

Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics

Architecture et lois d'échelle de l'endommagement tectonique associé aux failles : apports de données sur des systèmes de failles dans l'ouest américain

Seismogenic faults rupture intermittently, generating earthquakes of various magnitudes. These successive ruptures contribute to make the "master" fault grow, that is, accumulate displacements and gain in length over repeated seismic cycles. As a fault accumulates displacement, the embedding rocks are “damaged”, i.e., fractured at multiple locations around the master fault; a phenomenon referred to as “tectonic damage”. This tectonic damage predominantly consists of networks of fractures and secondary faults of different scales. This damage fracturing modifies the mechanical properties of the fault embedding rocks, and it has been shown that these rheological modifications influence the earthquake rupture dynamics, with, among others, acceleration of the rupture, amplification of the coseismic slips, etc. Characterizing the tectonic damage associated to faults is therefore important to understand and model its impact on earthquake rupture. My work contributes to address this topic. I have analyzed the architecture and other properties of tectonic damage in a large number of natural fault cases, spanning a broad range of lengths, cumulative displacements, slip modes, and degrees of structural maturity. Most of the analyzed fault systems are located in the western USA, and expose at the ground surface the traces of the secondary faults and fractures that form their damage zones. I analyzed these fault zones using a combination of optical remote images and topographic data, including Pléiades satellite images, drone and ground-based photogrammetric data, Lidar data, and field measurements. I mapped these fault zones at the highest possible resolutions to identify the macroscopic structures within the damage zones. I then used these high-resolution maps to measure a number of key parameters describing the damage structures and zones, such as their length, cumulative displacement, distance from and orientation relative to the master fault, among others. Measuring displacements was challenging, which led me to develop an innovative Matlab code, Auto_Throw, to automate the rigorous measure of vertical displacements on normal (i.e., extensive) faults in topographic data, along with their uncertainties. My application of Auto_Throw to multiple faults of various lengths confirmed certain generic properties of fault displacement distributions, revealed new generic properties (such as the systematic lateral variations in fault dips), and allowed me to develop a novel approach to measure the width of the innermost damage zone off a fault. In a second step, using the entire dataset of high-resolution fault maps, I developed a novel approach to identify, define and discriminate “inner” and “outer” damage zones. This led me to measure again a number of key parameters describing the damage structures and zones. Collectively, these measures reveal a number of scaling laws that describe the distribution, architecture and slip budget of the damage zones with respect to major properties of the parent fault (length, cumulative displacement, lateral segmentation, segment length, etc.). My work eventually shows that inner and outer damage zones significantly differ in distribution, width, composition (density, size and orientation of structures) and amount of accommodated displacements. The scaling laws I could suggest are key to better estimate the mechanical properties of the damaged rocks around faults, and to better represent fault zones in earthquake models.Les failles dites sismogènes rompent par intermittence en produisant des séismes de magnitudes diverses. Ces ruptures successives contribuent à la croissance de la faille « mère », qui accommode des déplacements cumulés croissants et s'allonge généralement au cours des temps géologiques. La croissance des failles endommage de façon permanente les roches encaissantes en les fracturant à différents endroits autour de la faille mère. Cette fracturation, dite d'endommagement tectonique, comprend principalement des réseaux de fractures et de failles secondaires de différentes échelles. L'endommagement tectonique altère les propriétés mécaniques des roches encaissantes autour de la faille mère, et il a été montré que ces modifications rhéologiques impactent le comportement de la rupture sismique (accélération de la rupture, amplification du glissement cosismique, etc.). Caractériser l'endommagement tectonique associé aux failles est donc important pour comprendre et modéliser son impact sur la rupture sismique. Ainsi, dans ce travail de thèse, j'ai analysé l'architecture de l'endommagement tectonique autour d'un grand nombre de failles naturelles ayant des longueurs, des déplacements cumulés, des modes de glissement, et un degré de maturité structurale variés. La plupart des systèmes de failles se situent dans l'Ouest américain, et exposent à la surface du sol la trace des failles secondaires et fractures formant leurs zones d'endommagement. J'ai donc analysé ces zones de failles à partir d'images aéro-spatiales optiques et de données topographiques (images satellitaires Pléiades, photogrammétrie par drone ou au sol, données Lidar), et de mesures de terrain. J'ai d'abord cartographié ces zones de failles aux plus hautes résolutions possibles, afin d'identifier l'essentiel des structures macroscopiques impliquées dans les zones d'endommagement. J'ai ensuite mesuré un certain nombre de paramètres définissant ces structures, i.e., longueur, déplacement accumulé, distance et orientation par rapport à la faille mère, etc. La mesure des déplacements s'est avérée complexe et m'a amené à développer un code innovant automatisant la mesure rigoureuse des déplacements verticaux sur les failles « normales » (i.e., extensives). L'application de ce code à de multiples failles de longueurs différentes a confirmé certaines propriétés génériques des distributions de déplacement sur les failles, révélé d'autres propriétés génériques jusqu'alors inconnues (variations latérales du pendage des failles), et permis de développer une nouvelle approche pour mesurer la largeur de la zone d'endommagement interne (inner damage) au plus près de la faille. Par ailleurs, l'examen de l'ensemble des données m'a permis de développer une nouvelle approche pour identifier, définir et discriminer ce que j'ai appelé les zones internes (inner damage) et externes (outer damage) de l'endommagement tectonique. L'application de cette approche aux données disponibles révèle un certain nombre de lois d'échelle décrivant la distribution, l'architecture et la cinématique des zones endommagées en regard de certaines propriétés de la faille mère (déplacement cumulé, segmentation latérale, longueur des segments, etc.). Les zones d'endommagement internes et externes sont différentes, tant en distribution et largeur, qu'en composition (densité, taille et orientation des structures) et quantités de déplacements accommodés. Ces lois d'échelles devraient permettre de mieux estimer les propriétés mécaniques des roches endommagées autour des failles, et représenter les systèmes de failles de façon plus réalistes dans les modèles de rupture

Architecture et lois d'échelle de l'endommagement tectonique associé aux failles : apports de données sur des systèmes de failles dans l'ouest américain

Seismogenic faults rupture intermittently, generating earthquakes of various magnitudes. These successive ruptures contribute to make the "master" fault grow, that is, accumulate displacements and gain in length over repeated seismic cycles. As a fault accumulates displacement, the embedding rocks are “damaged”, i.e., fractured at multiple locations around the master fault; a phenomenon referred to as “tectonic damage”. This tectonic damage predominantly consists of networks of fractures and secondary faults of different scales. This damage fracturing modifies the mechanical properties of the fault embedding rocks, and it has been shown that these rheological modifications influence the earthquake rupture dynamics, with, among others, acceleration of the rupture, amplification of the coseismic slips, etc. Characterizing the tectonic damage associated to faults is therefore important to understand and model its impact on earthquake rupture. My work contributes to address this topic. I have analyzed the architecture and other properties of tectonic damage in a large number of natural fault cases, spanning a broad range of lengths, cumulative displacements, slip modes, and degrees of structural maturity. Most of the analyzed fault systems are located in the western USA, and expose at the ground surface the traces of the secondary faults and fractures that form their damage zones. I analyzed these fault zones using a combination of optical remote images and topographic data, including Pléiades satellite images, drone and ground-based photogrammetric data, Lidar data, and field measurements. I mapped these fault zones at the highest possible resolutions to identify the macroscopic structures within the damage zones. I then used these high-resolution maps to measure a number of key parameters describing the damage structures and zones, such as their length, cumulative displacement, distance from and orientation relative to the master fault, among others. Measuring displacements was challenging, which led me to develop an innovative Matlab code, Auto_Throw, to automate the rigorous measure of vertical displacements on normal (i.e., extensive) faults in topographic data, along with their uncertainties. My application of Auto_Throw to multiple faults of various lengths confirmed certain generic properties of fault displacement distributions, revealed new generic properties (such as the systematic lateral variations in fault dips), and allowed me to develop a novel approach to measure the width of the innermost damage zone off a fault. In a second step, using the entire dataset of high-resolution fault maps, I developed a novel approach to identify, define and discriminate “inner” and “outer” damage zones. This led me to measure again a number of key parameters describing the damage structures and zones. Collectively, these measures reveal a number of scaling laws that describe the distribution, architecture and slip budget of the damage zones with respect to major properties of the parent fault (length, cumulative displacement, lateral segmentation, segment length, etc.). My work eventually shows that inner and outer damage zones significantly differ in distribution, width, composition (density, size and orientation of structures) and amount of accommodated displacements. The scaling laws I could suggest are key to better estimate the mechanical properties of the damaged rocks around faults, and to better represent fault zones in earthquake models.Les failles dites sismogènes rompent par intermittence en produisant des séismes de magnitudes diverses. Ces ruptures successives contribuent à la croissance de la faille « mère », qui accommode des déplacements cumulés croissants et s'allonge généralement au cours des temps géologiques. La croissance des failles endommage de façon permanente les roches encaissantes en les fracturant à différents endroits autour de la faille mère. Cette fracturation, dite d'endommagement tectonique, comprend principalement des réseaux de fractures et de failles secondaires de différentes échelles. L'endommagement tectonique altère les propriétés mécaniques des roches encaissantes autour de la faille mère, et il a été montré que ces modifications rhéologiques impactent le comportement de la rupture sismique (accélération de la rupture, amplification du glissement cosismique, etc.). Caractériser l'endommagement tectonique associé aux failles est donc important pour comprendre et modéliser son impact sur la rupture sismique. Ainsi, dans ce travail de thèse, j'ai analysé l'architecture de l'endommagement tectonique autour d'un grand nombre de failles naturelles ayant des longueurs, des déplacements cumulés, des modes de glissement, et un degré de maturité structurale variés. La plupart des systèmes de failles se situent dans l'Ouest américain, et exposent à la surface du sol la trace des failles secondaires et fractures formant leurs zones d'endommagement. J'ai donc analysé ces zones de failles à partir d'images aéro-spatiales optiques et de données topographiques (images satellitaires Pléiades, photogrammétrie par drone ou au sol, données Lidar), et de mesures de terrain. J'ai d'abord cartographié ces zones de failles aux plus hautes résolutions possibles, afin d'identifier l'essentiel des structures macroscopiques impliquées dans les zones d'endommagement. J'ai ensuite mesuré un certain nombre de paramètres définissant ces structures, i.e., longueur, déplacement accumulé, distance et orientation par rapport à la faille mère, etc. La mesure des déplacements s'est avérée complexe et m'a amené à développer un code innovant automatisant la mesure rigoureuse des déplacements verticaux sur les failles « normales » (i.e., extensives). L'application de ce code à de multiples failles de longueurs différentes a confirmé certaines propriétés génériques des distributions de déplacement sur les failles, révélé d'autres propriétés génériques jusqu'alors inconnues (variations latérales du pendage des failles), et permis de développer une nouvelle approche pour mesurer la largeur de la zone d'endommagement interne (inner damage) au plus près de la faille. Par ailleurs, l'examen de l'ensemble des données m'a permis de développer une nouvelle approche pour identifier, définir et discriminer ce que j'ai appelé les zones internes (inner damage) et externes (outer damage) de l'endommagement tectonique. L'application de cette approche aux données disponibles révèle un certain nombre de lois d'échelle décrivant la distribution, l'architecture et la cinématique des zones endommagées en regard de certaines propriétés de la faille mère (déplacement cumulé, segmentation latérale, longueur des segments, etc.). Les zones d'endommagement internes et externes sont différentes, tant en distribution et largeur, qu'en composition (densité, taille et orientation des structures) et quantités de déplacements accommodés. Ces lois d'échelles devraient permettre de mieux estimer les propriétés mécaniques des roches endommagées autour des failles, et représenter les systèmes de failles de façon plus réalistes dans les modèles de rupture

Architettura strutturale e zone di danneggiamento in zone di trasferimento in sistemi di faglie normali: il caso di studio di Vecchiano (PI) e modellizzazione sperimentale.

La segmentazione lungo la direzione è una caratteristica comune nelle faglie, particolarmente in regime estensionale. Le zone di trasferimento tra due segmenti indipendenti vengono definite relay zone e mostrano una strutturazione d’insieme caratterizzata da un’architettura complessa e da un’estesa zona di danneggiamento o damage zone. Vari esempi naturali mostrano evidenze di step tra faglie normali che bordano bacini in contesti tettonici estensionali. Oggetto di studio è stata l’analisi morfostrutturale del sistema di faglie normali di Vecchiano (PI), ove un’ampia zona di danneggiamento esumata è associabile ad uno step tra le due faglie principali che delimitano il margine orientale del bacino di Viareggio. Utilizzando un dataset ad elevata risoluzione (immagini LiDAR, ortofoto, DTM), si è proceduto ad una fotointerpretazione, tramite la quale è stata definita l’architettura strutturale d’insieme del sistema e i pattern di segmentazione lungo strike alla mesoscala, associati alla strutturazione di prim’ordine del bacino. Tali risultati sono stati analizzati quantitativamente tramite i software ArcMap e ArcScene in ambiente 2D e 3D, permettendo, in tal modo, la compilazione di un database delle scarpate di faglia, con rispettiva identificazione dei caratteri strutturali quali lunghezza e rigetto, plottati in diagrammi throw/lenght per ogni segmento, in grado di evidenziarne le variazioni lungo strike. L’analisi morfostrutturale è stata preceduta da un rilevamento geologico-strutturale sul terreno che ha integrato i dati già disponibili (rilevamenti inediti, Molli 1999-2009) con altri originali, sintetizzati in una carta in scala 1:10000. Lo studio del sistema di deformazione naturale è stato integrato con la realizzazione di una serie di modelli analogici, in contesto tettonico estensionale, realizzati presso i laboratori di modellizzazione sperimentale del Dipartimento di ‘’Gèosciences de l’Universitè de Montpellier II’’: l’obiettivo principale è stato quello di implementare le conoscenze riguardo l’evoluzione delle strutture deformative in zone di relay. Il setup proposto ha previsto l’imposizione di una discontinuità di velocità basale, agente su un layer dal comportamento elastico-frizionale, sulla quale vengono modellati due step di dimensioni variabili, rappresentanti eredità strutturali che influenzano il processo estensionale. Lo scopo è stato duplice: da un lato la caratterizzazione dell’architettura di prim’ordine e dell’evoluzione delle relay zones, in un modello sperimentale per il quale sono note le condizioni al contorno, e dall’altre la definizione dell’influenza sul sistema di parametri variabili nei diversi setting, riconosciuti come importanti fattori di controllo, quali: dimensionamento e morfologia degli step imposti, spessore del materiale analogo utilizzato, effetto della compattazione. I risultati principali dello studio riguardano l'influenza delle discontinuità basali nello sviluppo cinematico del sistema. Inoltre le analogie tra il caso di studio naturale di Vecchiano e quelli sperimentali hanno fornito informazioni significative sulla possibile evoluzione cinematica e significato tettonico delle strutture in zone di step in sistemi di faglie normali

The Complexity of Food Systems: Defining Relevant Attributes and Indicators for the Evaluation of Food Supply Chains in Spain

The wide-ranging literature on food systems provides multiple perspectives and world views. Various stakeholders define food and food systems in non-equivalent ways. The perception of the performance of food systems is determined by these specific perspectives, and a wide variety of policies responding to different aims are proposed and implemented accordingly. This paper sets out to demonstrate that the pre-analytical adoption of different narratives about the food system leads to non-equivalent assessments of the performance of food supply chains. In order to do so, we (i) identify a set of relevant narratives on food supply chains in Spanish and Catalan contexts; (ii) identify the pertinent attributes needed to describe and represent food supply chains within the different perspectives or narratives; and (iii) carry out an integrated assessment of three organic tomato supply chains from the different perspectives. In doing so, the paper proposes an analysis of narratives to enable the analyst to characterize the performance of food supply chains from different perspectives and to identify the expected trade-offs of integrated assessment, associating them with the legitimate-but-contrasting views found among the social actors involved

The Complexity of Food Systems: Defining Relevant Attributes and Indicators for the Evaluation of Food Supply Chains in Spain

© 2016 by the authors.The wide-ranging literature on food systems provides multiple perspectives and world views. Various stakeholders define food and food systems in non-equivalent ways. The perception of the performance of food systems is determined by these specific perspectives, and a wide variety of policies responding to different aims are proposed and implemented accordingly. This paper sets out to demonstrate that the pre-analytical adoption of different narratives about the food system leads to non-equivalent assessments of the performance of food supply chains. In order to do so, we (i) identify a set of relevant narratives on food supply chains in Spanish and Catalan contexts; (ii) identify the pertinent attributes needed to describe and represent food supply chains within the different perspectives or narratives; and (iii) carry out an integrated assessment of three organic tomato supply chains from the different perspectives. In doing so, the paper proposes an analysis of narratives to enable the analyst to characterize the performance of food supply chains from different perspectives and to identify the expected trade-offs of integrated assessment, associating them with the legitimate-but-contrasting views found among the social actors involved.This work has been carried out within the framework of the EU FP7 research project “Global and Local food chain Assessment: a Multidimensional performance-based approach (GLAMUR)” (KBBE.2012.2.5-03—Grant Agreement No.: 311778). The European Union or the European Union Commission cannot be held responsible for results and opinions quoted in the text. The research of Gonzalo Gamboa is funded by the Spanish National project HAR2013-47182-C02-01 and the Catalan Research group 2014SGR591. Marta G. Rivera-Ferre is funded by the Ramon y Cajal fellowships programPeer reviewe