Slope analysis of active fault in volcanic areas using high-resolution DEM based on GIS

2020 ◽  
Author(s):  
Daisaku Kawabata ◽  
Haruo Kimura
Keyword(s):  
High Resolution ◽  
Active Faults ◽  
Volcanic Rocks ◽  
Surface Displacement ◽  
Strike Slip ◽  
Slope Aspect ◽  
Target Area ◽  
Fault Activity ◽  
Lateral Strike Slip ◽  
The Relationship

<p>The movement of active faults due to inland earthquakes often involves surface displacement. In Japan, where many active faults are distributed, fault displacements are often accumulated and reflected on the current topography. For example, in a region where right-lateral strike-slip faults are distributed, it is possible to observe river topography systematically right-lateral strike-slip from the fault. Japan has many volcanoes as well as active faults, but in volcanic areas it is difficult to find evidence of fault activity accumulation in the terrain, and it is difficult to find fault traces on the surface. In this study, we performed geomorphological analysis using high-resolution DEM based on GIS in the southern part of Iwate prefecture where many volcanic rocks are distributed, and examined the relationship between river topography and active faults. The target area is mainly covered by Miocene to Pleistocene volcanic rocks. In this area, despite significant earthquakes occurring since 1896, there is little apparent surface displacement. An Mw 6.9 earthquake with surface displacement occurred in 2008 in this area. In this study, basic topographical measurements such as slope, aspect, dispersion of altitude, and stream density and stream-power indices were analyzed using 5mDEM in the target area. As a result, it was found that the SPI value tends to be higher in the area where surface displacement was observed in 2008. It is necessary to clarify the relationship between fault activity and topography by increasing the target area and conducting watershed analysis using SPI and other indices.</p>

Joint multidisciplinary study of the Saint-Sauveur–Donareo fault (lower Var valley, French Riviera): a contribution to seismic hazard assessment in the urban area of Nice

2011 ◽  
Vol 182 (4) ◽  
pp. 323-336 ◽  
Author(s):  
Christophe Larroque ◽  
Bertrand Delouis ◽  
Jean-Claude Hippolyte ◽  
Anne Deschamps ◽  
Thomas Lebourg ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Urban Areas ◽  
Regional Scale ◽  
Active Faults ◽  
Focal Depth ◽  
Strike Slip ◽  
Fault System ◽  
Geophysical Investigation ◽  
Lateral Strike Slip ◽  
North East

AbstractThe lower Var valley is the only large outcropping zone of Plio-Quaternary terrains throughout the southwestern Alps. In order to assess the seismic hazard for the Alps – Ligurian basin junction, we investigated this area to provide a record of earthquakes that have recently occurred near the city of Nice. Although no historical seismicity has been indicated for the lower Var valley, our main objective was to identify traces of recent faulting and to discuss the seismogenic potential of any active faults. We organized multidisciplinary observations as a microseismic investigation (the PASIS survey), with morphotectonic mapping and imagery, and subsurface geophysical investigations. The results of the PASIS dense recording survey were disappointing, as no present-day intense microseismic activity was recorded. From the morphotectonic investigation of the lower Var valley, we revealed several morphological anomalies, such as drainage perturbations and extended linear anomalies that are unrelated to the lithology. These anomalies strike mainly NE-SW, with the major Saint-Sauveur – Donareo lineament, clearly related to faulting of the Plio-Pleistocene sedimentary series. Sub-surface geophysical investigation (electrical resistivity tomography profiling) imaged these faults in the shallow crust, and together with the microtectonic data, allow us to propose the timing of recent faulting in this area. Normal and left-lateral strike-slip faulting occurred several times during the Pliocene. From fault-slip data, the last episode of faulting was left-lateral strike-slip and was related to a NNW-SSE direction of compression. This direction of compression is consistent with the present-day state of stress and the Saint-Sauveur–Donareo fault might have been reactivated several times as a left-lateral fault during the Quaternary. At a regional scale, in the Nice fold-and-thrust belt, these data lead to a reappraisal of the NE-SW structural trends as the major potentially active fault system. We propose that the Saint-Sauveur–Donareo fault belongs to a larger system of faults that runs from near Villeneuve-Loubet to the southwest to the Vésubie valley to the north-east. The question of a structural connection between the Vésubie – Mt Férion fault, the Saint-Sauveur–Donareo fault and its possible extension offshore through the northern Ligurian margin is discussed.The Saint-Sauveur–Donareo fault shows two en-échelon segments that extend for about 8 km. Taking into account the regional seismogenic depth (about 10 km), this fault could produce M ~6 earthquakes if activated entirely during one event. Although a moderate magnitude generally yields a moderate seismic hazard, we suggest that this contribution to the local seismic risk is high, taking into account the possible shallow focal depth and the high vulnerability of Nice and the surrounding urban areas.

New 3D Pg and Sg Velocity Models for High-Resolution Seismotectonic Interpretations in the Central Alps

2020 ◽  
Author(s):  
Tobias Diehl ◽  
Edi Kissling ◽  
Timothy Lee ◽  
Stefan Schmid ◽  
Marco Herwegh
Keyword(s):  
High Resolution ◽  
Sedimentary Cover ◽  
Active Faults ◽  
Ground Truth ◽  
Strike Slip ◽  
Crystalline Basement ◽  
Central Alps ◽  
Phase Selection ◽  
Velocity Models ◽  
Aar Massif

<p>The present-day deformation in the Central Alps is dominated by vertical uplift, at rates up to 1.5 mm/yr as indicated by high-precision levelling and GPS data. Understanding the driving mechanisms of this neotectonic uplift and its link to seismicity in the Central Alps requires accurate locations of current deformation processes within the upper crust. Especially the question if and how deformation in the crystalline basement is coupled with deformation in the overlaying nappe systems is key to understand the neotectonic processes. Seismicity provides important information on deformation in the uppermost crust, however, an accuracy of focal depths in the order of few kilometers and less is required to distinguish sources in the basement from sources in the sedimentary cover.</p><p>In this study, we demonstrate how insufficient crustal velocity models and inconsistent seismic phase selection can lead to biased hypocenter solutions, which hamper such high-resolution seismotectonic interpretations. We propose a relocation procedure combining a new high-resolution Pg and Sg 3D crustal model of the Central Alps with a dynamic seismic phase selection to overcome this bias and to improve accuracy of hypocenter solutions. The new tomographic model is based on more than 60,000 Pg and 30,000 quality-checked Sg phases of earthquakes, which occurred in the greater Central Alpine region between 1996 and 2019. In combination with a nonlinear, probabilistic earthquake location algorithm, the model was used to relocate more than 18’000 earthquakes, which occurred in this region over the past 36 years. The derived catalog includes a consistent error and quality assessment, calibrated against ground-truth events like quarry blasts.</p><p>The relocated seismicity in the Central Alps is interpreted together with additional information from the tomographic model, focal mechanisms, geophysical, geological and geodetic data. We focus our interpretation on the eastern Aar massif as well as on the Rawil depression, located in-between the outcropping Aar and Aiguilles-Rouge massifs. Both regions were recently affected by remarkable seismic events. The ML4.6 Urnerboden earthquake of 2017 occurred near the eastern termination of the Aar massif, while a sequence of about 350 events occurred in the Rawil earthquake lineament near the Sanetschpass in November 2019. Both sequences provide unique insights into active faults in the Central Alps and we image systems of sub-vertically oriented strike-slip faults of variable strike, which root in the crystalline basement in both regions. Our results document the existence of active strike-slip fault systems in the External Crystalline Massifs of the Central Alps in regions of maximum change in uplift rates. We therefore discuss possible models relating the observed strike-slip kinematics to buoyancy-driven vertical tectonic processes.</p>

The Mt. Rainier earthquake of July 18, 1973, and its tectonic significance

1975 ◽  
Vol 65 (2) ◽  
pp. 393-401 ◽  
Author(s):  
Robert S. Crosson ◽  
David Frank
Keyword(s):  
Puget Sound ◽  
Active Faults ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Aerial Photographs ◽  
Tectonic Significance ◽  
Earthquake Generation ◽  
Surrounding Areas ◽  
Relationship Of ◽  
The Relationship

abstract On July 18, 1973, a magnitude 3.9 earthquake was strongly felt at Longmire and surrounding areas near Mt. Rainier, Washington. Network analysis permitted an accurate hypocenter to be located at 46°49.29′N and 121°49.86′W at a depth of 10.9 km, about 7 km southwest of the summit of Mt. Rainier. No prolonged aftershock sequence was generated, although two small aftershocks were recorded and located. Aerial photographs of the epicentral region reveal several northwest-trending lineaments which may be related to active faults in the region, although no surface ground breakage was discovered. The focal mechanism obtained for the main shock is well constrained and consistent with right-lateral strike-slip motion along a northwest-trending fracture, in general agreement with northwest-trending surface lineaments. The nature of the relationship of the earthquake occurrence to Mt. Rainier is uncertain. The principal compressive axis direction is in agreement with that found in the central Puget Sound basin. However, the shallow depths, the strike-slip mode of faulting, and the past evidence of earthquakes near Mt. Rainier suggest a direct relationship between faulting, earthquake generation, and the volcano location.

scholarly journals Source processes of large earthquakes along the Xianshuihe fault in southwestern China

1983 ◽  
Vol 73 (2) ◽  
pp. 537-551
Author(s):  
Huilan Zhou ◽  
Hsui-Lin Liu ◽  
Hiroo Kanamori
Keyword(s):  
Fault Zone ◽  
Body Wave ◽  
Active Faults ◽  
Strike Slip ◽  
The Body ◽  
Southwestern China ◽  
Total Moment ◽  
Lateral Strike Slip ◽  
Largest Aftershock ◽  
Large Earthquakes

abstract The Xianshuihe fault is one of the most active faults in southwestern China. Recently, three large earthquakes occurred along it in 1967 (Ms = 6.1), 1973 (Ms = 7.5), and 1981 (Ms = 6.8). The 1981 event occurred near the central portion of the fault zone. Modeling of the body and surface waves indicates pure left-lateral strike-slip motion on a vertical fault striking N40°W consistent with the surface trend of the Xianshuihe fault. Two major ruptures are suggested for this source, with a total moment of 1.3 ×1026 dyne-cm. The 1973 event occurred about 65 km northwest of the 1981 event and ruptured about 90 km bilaterally along the fault. The body-wave synthetics indicate three main ruptures during faulting within 43 sec, with a total moment of 1.8 ×1027 dyne-cm. The mechanisms are similar to the 1981 event, and the average slip is determined to be 3.8 m. The largest aftershock (Ms = 5.9) occurred 1 day after the main event with a normal-fault mechanism striking almost perpendicular to the surface breakage. The 1967 event occurred at the northwestern end of the fault zone, with a strike of N65°E. It had a nearly normalfault mechanism with a seismic moment of 4.5 ×1025 dyne-cm. The largest aftershock (Ms = 5.1) occurred 7 hr later with a similar focal mechanism. The primary faulting along the Xianshuihe fault is left-lateral strike-slip, but the normal faulting with strike direction about perpendicular to the Xianshuihe fault trace is common, especially in the northwestern segment. The faulting pattern in this region is consistent with the regional stress field caused by the India-Tibet collision. The normal event which is not on the major fault seems to have more frequent foreshocks and aftershocks than those on the main fault.

The Neogene Veracruz fault: evidences for left-lateral slip along the southern Mexico block

2008 ◽  
Vol 179 (2) ◽  
pp. 195-208 ◽  
Author(s):  
Louis Andreani ◽  
Claude Rangin ◽  
Juventino Martínez-Reyes ◽  
Charlotte Le Roy ◽  
Mario Aranda-García ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Structural Data ◽  
Strike Slip ◽  
Southern Mexico ◽  
Lateral Strike Slip ◽  
Middle America Trench ◽  
The North ◽  
Mexican Volcanic Belt ◽  
Trans Mexican Volcanic Belt

Abstract Structural data combined with analysis of satellite images and seismic profiles show that a major left-lateral strike-slip fault affects the Veracruz basin and post-5 Ma volcanic rocks of the Los Tuxtlas volcanic field (LTVF). The main volcanic alignment of the LTVF is located along this fault. Additional structural data collected in the Trans-Mexican volcanic belt (areas of Xalapa, Teziutlán and Huauchinango) show that the shear zone affects Pliocene Trans-Mexican volcanic rocks. Low seismicity associated to faulted Quaternary markers such as alluvial fans, alluvial terraces and volcanoes argue for active faulting in this area. Plio-Quaternary strike-slip faulting in the Veracruz basin and in the eastern Trans-Mexican volcanic belt is important because it connects two important structural provinces: the left-lateral strike-slip faults province to the south and the left-lateral transtensive faulting that affects the central part of the Trans-Mexican volcanic belt. These three active deformation zones constitute the boundary between the southern Mexico block and the North American plate. It is generally assumed that strike-slip faulting along the Trans-Mexican and Central America volcanic arcs is the result of oblique subduction of the Cocos plate under the North American and Caribbean plates. However slip vectors along the Middle America trench are almost perpendicular to the trench. This Neogene sinistral strike-slip motion could be partially driven by the eastward motion of the Caribbean plate rather than by strain partitioning along the oblique Middle America trench subduction zone.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Practical High Resolution Microscopy

1968 ◽  
Vol 26 ◽  
pp. 302-303
Author(s):  
P. A. Marsh ◽  
T. Mullens ◽  
D. Price
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Resolving Power ◽  
Careful Attention ◽  
Electron Microscopes ◽  
The Relationship ◽  
High Resolution Microscopy ◽  
New Facilities

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

Context-dependent relationship in high-resolution micro-ECoG studies during finger movements

2020 ◽  
Vol 132 (5) ◽  
pp. 1358-1366
Author(s):  
Chao-Hung Kuo ◽  
Timothy M. Blakely ◽  
Jeremiah D. Wander ◽  
Devapratim Sarma ◽  
Jing Wu ◽  
...  
Keyword(s):  
High Resolution ◽  
Sensorimotor Cortex ◽  
Index Finger ◽  
Hand Movement ◽  
Cortical Activation ◽  
Hand Movements ◽  
Finger Movements ◽  
Thumb Movement ◽  
Neurosurgical Patients ◽  
The Relationship

OBJECTIVEThe activation of the sensorimotor cortex as measured by electrocorticographic (ECoG) signals has been correlated with contralateral hand movements in humans, as precisely as the level of individual digits. However, the relationship between individual and multiple synergistic finger movements and the neural signal as detected by ECoG has not been fully explored. The authors used intraoperative high-resolution micro-ECoG (µECoG) on the sensorimotor cortex to link neural signals to finger movements across several context-specific motor tasks.METHODSThree neurosurgical patients with cortical lesions over eloquent regions participated. During awake craniotomy, a sensorimotor cortex area of hand movement was localized by high-frequency responses measured by an 8 × 8 µECoG grid of 3-mm interelectrode spacing. Patients performed a flexion movement of the thumb or index finger, or a pinch movement of both, based on a visual cue. High-gamma (HG; 70–230 Hz) filtered µECoG was used to identify dominant electrodes associated with thumb and index movement. Hand movements were recorded by a dataglove simultaneously with µECoG recording.RESULTSIn all 3 patients, the electrodes controlling thumb and index finger movements were identifiable approximately 3–6-mm apart by the HG-filtered µECoG signal. For HG power of cortical activation measured with µECoG, the thumb and index signals in the pinch movement were similar to those observed during thumb-only and index-only movement, respectively (all p > 0.05). Index finger movements, measured by the dataglove joint angles, were similar in both the index-only and pinch movements (p > 0.05). However, despite similar activation across the conditions, markedly decreased thumb movement was observed in pinch relative to independent thumb-only movement (all p < 0.05).CONCLUSIONSHG-filtered µECoG signals effectively identify dominant regions associated with thumb and index finger movement. For pinch, the µECoG signal comprises a combination of the signals from individual thumb and index movements. However, while the relationship between the index finger joint angle and HG-filtered signal remains consistent between conditions, there is not a fixed relationship for thumb movement. Although the HG-filtered µECoG signal is similar in both thumb-only and pinch conditions, the actual thumb movement is markedly smaller in the pinch condition than in the thumb-only condition. This implies a nonlinear relationship between the cortical signal and the motor output for some, but importantly not all, movement types. This analysis provides insight into the tuning of the motor cortex toward specific types of motor behaviors.

scholarly journals High-resolution relocation of aftershocks of the Mw7.1 Darfield, New Zealand, earthquake and implications for fault activity

2013 ◽  
Vol 118 (8) ◽  
pp. 4184-4195 ◽  
Author(s):  
E. M. Syracuse ◽  
C. H. Thurber ◽  
C. J. Rawles ◽  
M. K. Savage ◽  
S. Bannister
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Fault Activity
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