43 research outputs found
Data for: Regional Relative Tectonic Activity of Structures in the Pampean Flat Slab Segment of Argentina from 30 to 32°S
No full textGeomorphic Inices measurements from Faults in the Pampean Flat Slab Segment of Argentin
The Central Mindoro Fault: An Active Sinistral Fault Within the Translational Boundary Between the Palawan Microcontinental Block and the Philippine Mobile Belt
No full textThe NNW-trending Central Mindoro Fault (CMF) is an active oblique left-lateral strike-slip fault as determined from offset morphotectonic features such as spurs and streams. Mapping of the trace and determination of the sinistral strike-slip sense of motion of the CMF is essential not only to the assessment of hazards but also to providing a clearer perspective of its role in accommodating deformation resulting from the NW relative motion between the Philippine Sea Plate and the Sunda Plate. Its sense of motion is also kinematically congruent with the NW-SE translation along a transcurrent zone between the Philippine Mobile Belt and the Palawan Microcontinental Block on the western part of the Philippine archipelago. It is also consistent with the left-lateral motion of other structures within the zone, such as the Verde Passage Fault—another structure believed to be accommodating the NW-SE translation. Mapping of the CMF provides a key constraint in identifying the possible mechanism(s) involved in the dextral strike-slip motion of the 1994 Mindoro Earthquake ground rupture, which is subparallel to the CMF
Relative Uplift Rates Along the Central Mindoro Fault, Philippines
No full textThe Central Mindoro Fault (CMF) is a major active oblique, sinistral strike-slip fault within the Philippine archipelago that accommodates the oblique convergence between the Philippine Sea Plate (PSP) and the Sunda Plate (SP). This study focused on assessing the spatial distribution of relative uplift rates along the CMF by calculating multiple geomorphic indices (elongation ratio, volume-to-area-ratio, valley floor width-to-height ratio, hypsometric integral, and normalized steepness index) and interpreting these values in the context of any along-strike variations in geology and climate, as well as the context of the CMF’s kinematics. We observed 2 characteristics of spatial distributions of relative uplift rates: (1) at least 20–30 km-long high uplift rate sections in the northwestern end of the CMF-bound mountain range (CMF segment I), and (2) at most, CMF-wide moderate to high uplift rates. This trend matches the geomorphic-based cumulative fault offset measurements distribution, possibly indicating consistent kinematics and an overall nearly-uniform stress-field since at least the Pleistocene. Based on the spatial distribution of areas with high relative uplift rates highlighted by this study, future efforts to assess the CMF’s seismogenic capability should focus on segments I and III
Marikina Valley Fault Creeping Segment (Philippines) - Groundwater Extraction Data
No full textThis dataset contain information on groundwater extraction for different well locations along the creeping segment of the Marikina Valley Fault System (Philippines)
Distribution and Rates of Quaternary Deformation within the Pampean Flat Slab Segment of the Central Andes of Argentina from 30-32°S
No full textThe Pampean Flat Slab is characterized by a wide zone of active upper-plate deformation that involves both thin- and thick-skinned deformation. It provides a rare opportunity to explore the possible control of slab geometry, deformation style, and tectonic evolution of structures on upper-plate strain distribution; observe the distribution and relative proportions of shortening accommodated by Quaternary plate-boundary related and intraplate contractional deformation; compare the potential of these faults for generating devastating (≥ Mw 7) earthquakes; and apply geomorphic indices to analyze regional strain distribution patterns. This thesis provides valuable constraints on regional strain distribution for the Pampean Flat Slab since at least the Pleistocene, from both absolute and relative geomorphic slip rates. A shortening rate of ~0.4 mm/yr since Mid-Pleistocene was measured on the La Rinconada Fault Zone (LRFZ), which together with similarly low published slip rates on other regional faults is explained through nearly uniformly distributed strain in the predominantly thin-skinned Precordillera region. The LRFZ’s slip rate is associated with earthquake magnitudes of MW 6.6–7.2. In contrast, the much lower average shortening rate of ~0.2 mm/yr since the Mid-Pleistocene on the thick-skinned Las Chacras Fault Zone (LCFZ), located to the east of the LRFZ, suggests a possible W-E trend of decreasing shortening rates in the Pampean flat slab. Earthquake magnitudes of MW 6.7–7.1 estimated on the LCFZ shows that intraplate faults are equally capable of causing potentially devastating earthquakes. Relative slip rates from geomorphic indices exhibit a trend of W-E decreasing slip rates similar to that observed both in geodetic and neotectonic studies, indicating a possibly constant stress-field since at least the Pleistocene. This spatial correspondence in lowering of slip rates with the resumption of a more steeply subducting Nazca plate points to the first documented change in slip rates as a function of slab dip in the Pampean Flat Slab. Relative slip rates also pointed to sites requiring further detailed studies. Knowledge of the controls on active upper plate deformation in the Pampean Flat Slab segment therefore provides additional information for better understanding of the behavior and evolution of present-day and ancient flat slab settings worldwide.Ph.D
Distribution and Rates of Quaternary Deformation within the Pampean Flat Slab Segment of the Central Andes of Argentina from 30-32°S
No full textThe Pampean Flat Slab is characterized by a wide zone of active upper-plate deformation that involves both thin- and thick-skinned deformation. It provides a rare opportunity to explore the possible control of slab geometry, deformation style, and tectonic evolution of structures on upper-plate strain distribution; observe the distribution and relative proportions of shortening accommodated by Quaternary plate-boundary related and intraplate contractional deformation; compare the potential of these faults for generating devastating (≥ Mw 7) earthquakes; and apply geomorphic indices to analyze regional strain distribution patterns. This thesis provides valuable constraints on regional strain distribution for the Pampean Flat Slab since at least the Pleistocene, from both absolute and relative geomorphic slip rates. A shortening rate of ~0.4 mm/yr since Mid-Pleistocene was measured on the La Rinconada Fault Zone (LRFZ), which together with similarly low published slip rates on other regional faults is explained through nearly uniformly distributed strain in the predominantly thin-skinned Precordillera region. The LRFZ’s slip rate is associated with earthquake magnitudes of MW 6.6–7.2. In contrast, the much lower average shortening rate of ~0.2 mm/yr since the Mid-Pleistocene on the thick-skinned Las Chacras Fault Zone (LCFZ), located to the east of the LRFZ, suggests a possible W-E trend of decreasing shortening rates in the Pampean flat slab. Earthquake magnitudes of MW 6.7–7.1 estimated on the LCFZ shows that intraplate faults are equally capable of causing potentially devastating earthquakes. Relative slip rates from geomorphic indices exhibit a trend of W-E decreasing slip rates similar to that observed both in geodetic and neotectonic studies, indicating a possibly constant stress-field since at least the Pleistocene. This spatial correspondence in lowering of slip rates with the resumption of a more steeply subducting Nazca plate points to the first documented change in slip rates as a function of slab dip in the Pampean Flat Slab. Relative slip rates also pointed to sites requiring further detailed studies. Knowledge of the controls on active upper plate deformation in the Pampean Flat Slab segment therefore provides additional information for better understanding of the behavior and evolution of present-day and ancient flat slab settings worldwide.Ph.D
Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines
No full textThe Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately
Tectonic geomorphology of the Ottawa-Bonnechere Graben, Eastern Canada: implications for regional uplift and intraplate seismicity
No full textIn intraplate areas where regional tectonic strain is accommodated by reactivation of pre-existing structures, the level of seismic hazard associated with faults in may be underestimated due to the poor surface expression of faults, scattered earthquake distribution, and long earthquake recurrence intervals. The cause of seismicity in eastern Canada remains unresolved. This is partially because surface expression of faults have been eroded during glacial and deglacial periods and in many cases are undetectable until a seismic event. Morphotectonic analysis has been widely applied to assess relative tectonic activity in various geological settings. To establish whether active uplift is occurring and to investigate the spatial distribution of uplift rates, 131 bedrock drainage basins in the Ottawa-Bonnechere Graben (OBG) were analysed. The aim of this was to: 1) test the applicability of geomorphic indices for quantifying active deformation, 2) quantify the spatiotemporal distribution of relative uplift rates, and 3) explore the implications for faulting mechanisms, deformation styles, and ultimately regional seismic hazard. We measured valley floor width-to-height ratio (Vf), basin elongation ratio (Re), basin hypsometric integral (HI), and normalized channel steepness index (ksn). The results demonstrate that high relative uplift rates occur in all six bedrock escarpment sections studied and suggests that are possibly associated with regional broad wavelength uplift (epeirogeny) resulting from a likely complex interaction between far field tectonic stress and glacial isostatic adjustment (GIA). Our analysis showed that Vf, Re, and ksn reveals no considerable spatial differences in high relative uplift rates, consistent with the Canadian base network GPS uplift rates.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Late Quaternary Activity of the La Rinconada Fault Zone, San Juan, Argentina
No full textMost of the permanent deformation in the Pampean Flat slab segment of the central Andes is taken up at the Andean Orogenic Front in Argentina, a narrow zone between the Eastern Precordillera and Sierras Pampeanas that comprises one of the world's most seismically active thrust zones. Active faults and folds in the region have been extensively mapped but still largely lack information on style and rates of deformation, which is essential for understanding the distribution of regional strain and estimating the seismic potential of individual faults. Structural, geomorphic, and 36Cl cosmogenic radionuclide surface exposure age methods are used to focus on key sites along the 30-km-long La Rinconada Fault Zone in this region of west-central Argentina, which is ~15 km away from the highly populated (~500,000) city of San Juan, to define a late Quaternary average shortening rate of 0.41 ± 0.01 mm/year. This slip rate is the same order of magnitude, but slightly lower than nearby similar east dipping Eastern Precordillera faults including the La Laja and Las Tapias Faults. Relatively low slip rates are interpreted as being a consequence of distributed deformation between the latitude of the La Rinconada Fault Zone (31 and 32°S), as compared to between latitudes 32 to 33°S where deformation appears to be focused on fewer structures, including the Las Peñas and La Cal Thrust Faults. The La Rinconada Fault Zone is capable of generating earthquakes of Mw 6.6–7.2, but further investigations are required to determine timing and recurrence intervals of discrete events.Fil: Rimando, Jeremy. University of Toronto; CanadáFil: Schoenbohm, Lindsay. University of Toronto; CanadáFil: Costa, Carlos Horacio. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Owen, Lewis. University of Cincinnati; Estados UnidosFil: Cesta, Jason M.. University of Cincinnati; Estados UnidosFil: Richard, Andrés David. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; ArgentinaFil: Gardini, Carlos Enrique. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentin
Complex Shear Partitioning Involving the 6 February 2012 MW 6.7 Negros Earthquake Ground Rupture in Central Philippines
No full textA 75 km-long, generally NE-striking ground rupture associated with the 6 February 2012 MW 6.7 (Mb 6.9) Negros earthquake was mapped on the eastern side of Negros Island, Philippines. It closely follows a previously unmapped, pre-existing fault trace along the coast which is marked mostly by terrace-forming scarps. The dominance of vertical separation (west side up) is consistent with a west-dipping reverse fault, as indicated by focal mechanism solutions. The ground rupture map eliminates the ambiguity in the focal mechanism solution regarding the orientation, sense of motion, and location of the seismogenic fault plane, which are indispensable in the assessment of seismic hazards and the nature and distribution of deformation. This study uses the ground rupture map of the 2012 Negros earthquake in sorting out the mechanism of deformation in the Visayas Islands region. The ground rupture’s length is well within the aftershock area while its scarp heights are consistent with an earthquake of its magnitude and nature of movement. The 2012 Negros earthquake rupture’s pattern, scarp types, and offset of man-made structures are similar to those of recent reverse/thrust ground ruptures mapped globally and are distinct from those associated with erosion, landslide, and liquefaction. The onshore coseismic reverse fault of the Negros earthquake, which contradicts a model of coseismic slip on an offshore blind thrust fault by previous workers, represents the first thoroughly mapped ground rupture of its kind in the Philippines. The ground ruptures of the 2012 Negros and 2013 Bohol earthquakes, along with the Philippine Trench and the Philippine Fault Zone (PFZ), represent a complex shear partitioning mechanism in the Visayas Islands region. This departs from the current simple shear partitioning model for the region and is distinct from those for other regions along the PFZ and adjacent subduction zones. This study shows how an appreciation of morphotectonic features can lead to a better understanding of the distribution of deformation and the nature of earthquake hazards
