Quaternary deformation of the Bajo Segura blind fault (eastern Betic Cordillera, Spain) revealed by high-resolution reflection profiling

2002 ◽  
Vol 139 (3) ◽  
pp. 331-341 ◽  
Author(s):  
P. ALFARO ◽  
J. M. ANDREU ◽  
J. M. ANDREU ◽  
A. ESTÉVEZ ◽  
J. M. SORIA ◽  
...  
Keyword(s):  
High Resolution ◽  
Complex Geometry ◽  
Surface Expression ◽  
Seismic Profile ◽  
Betic Cordillera ◽  
Reverse Fault ◽  
Seismic Profiles ◽  
Growth Strata ◽  
Quaternary Deformation ◽  
Splay Faults

The blind reverse Bajo Segura Fault is located at the eastern extreme of the Trans-Alboran shear zone (Betic Cordillera, southeast Iberian Peninsula). The surface expression of recent activity of this blind ENE–WSW fault is represented by coseismic surface anticlines and growth synclines on both sides of the anticlines. In the synclines, the deformation of the most recent Quaternary materials is obscured by a sedimentary unit more than 30 m thick which was deposited during the later part of the Late Pleistocene and the Holocene. The present study reports three high-resolution seismic profiles made in the northern growth syncline, which was the one developed most by the Bajo Segura Fault. In these seismic profiles we recognize the boundary between pre-growth strata and growth strata. This marker, Early Pliocene in age, dates the start of the activity of this blind reverse fault. The geometry observed in the seismic profiles of the syntectonic strata, dating from the Late Pliocene and Quaternary, indicates a limb rotation folding mechanism. On seismic profile 2, the complex geometry of the Benejúzar anticline forelimb can be attributed to several splay faults close to the surface of Bajo Segura Fault.

Quality control and risk assessment of seismic profiles using area-depth-strain analysis

2015 ◽  
Vol 3 (4) ◽  
pp. SAA1-SAA15 ◽  
Author(s):  
Richard H. Groshong
Keyword(s):  
Quality Control ◽  
Numerical Models ◽  
Strain Analysis ◽  
Seismic Profile ◽  
Seismic Profiles ◽  
Growth Strata ◽  
Structural Style ◽  
Before And After ◽  
Fault Bend ◽  
Detachment Fold

Area-depth-strain (ADS) analysis is a method for quantifying the structural style, balance, boundary displacement, detachment locations, and subseismic strain from a seismic profile, information that is particularly useful for quality control and risk analysis. The method is based on measurements of excess area, width, depth, and bed length of multiple horizons in a structure. A balanced structure is indicated by a well-defined line or lines on an area-depth graph. The structural uncertainty or risk of the interpretation is quantified using the fit of the data to the least-squares line(s), the match between the ADS detachment values and the interpreted geometry, and the magnitudes of the calculated strains. The method also clearly separates syntectonic (growth) units from nontectonic (pregrowth and no-growth) units. Different area-depth graph styles represent (1) classic detachment folds, fault-propagation folds, and ramp anticlines; (2) buckle-style detachment folds; and (3) fault-bend folds. The focus here is on the first two. Numerical models of the detachment fold styles show the similarities and differences between their geometries and ADS interpretations. Both styles are evaluated with seismic profiles across oilfield-scale structures. The Alpha/Bobo field, Nigeria, is a classic detachment fold, and an Angolan anticline is of the buckle style. Profiles across the Alpha/Bobo field before and after the first well was drilled demonstrate the improvement in the ADS interpretation of the lower detachment location and the reduction of layer-parallel strains in the revised profile. The Alpha/Bobo field and the Angola fold illustrate the distinction between growth and no-growth intervals and the interpretation of growth strata. Both fields show the use of predicted versus observed ADS results to suggest possible improvements to the interpretation.

scholarly journals Progressive Degradation of an Ice Rumple in the Thwaites Ice Shelf, Antarctica, as Observed from High-Resolution Digital Elevation Models

2018 ◽  
Vol 10 (8) ◽  
pp. 1236 ◽  
Author(s):  
Seung Hee Kim ◽  
Duk-jin Kim ◽  
Hyun-Cheol Kim
Keyword(s):  
High Resolution ◽  
Surface Deformation ◽  
Surface Expression ◽  
Deformation Model ◽  
Ice Shelf ◽  
Pressure Source ◽  
Viscoelastic Deformation ◽  
Shelf Stability ◽  
Transient Nature ◽  
Elevation Changes

Ice rumples are locally-grounded features of flowing ice shelves, elevated tens of meters above the surrounding surface. These features may significantly impact the dynamics of ice-shelf grounding lines, which are strongly related to shelf stability. In this study, we used TanDEM-X data to construct high-resolution DEMs of the Thwaites ice shelf in West Antarctica from 2011 to 2013. We also generated surface deformation maps which allowed us to detect and monitor the elevation changes of an ice rumple that appeared sometime between the observations of a grounding line of the Thwaites glacier using Double-Differential Interferometric SAR (DDInSAR) in 1996 and 2011. The observed degradation of the ice rumple during 2011–2013 may be related to a loss of contact with the underlying bathymetry caused by the thinning of the ice shelf. We subsequently used a viscoelastic deformation model with a finite spherical pressure source to reproduce the surface expression of the ice rumple. Global optimization allowed us to fit the model to the observed deformation map, producing reasonable estimates of the ice thickness at the center of the pressure source. Our conclusion is that combining the use of multiple high-resolution DEMs and the simple viscoelastic deformation model is feasible for observing and understanding the transient nature of small ice rumples, with implications for monitoring ice shelf stability.

Morphology and geological setting of Iseo Lake (Lombardy) through multibeam bathymetry and high-resolution seismic profiles

2007 ◽  
Vol 100 (1) ◽  
pp. 23-40 ◽  
Author(s):  
Alfredo Bini ◽  
Daniele Corbari ◽  
Paolo Falletti ◽  
Mauro Fassina ◽  
Cesare R. Perotti ◽  
...  
Keyword(s):  
High Resolution ◽  
Multibeam Bathymetry ◽  
Seismic Profiles ◽  
Geological Setting

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

Multiscale seismic imaging of active fault zones for hazard assessment: A case study of the Santa Monica fault zone, Los Angeles, California

Geophysics ◽  
1998 ◽  
Vol 63 (2) ◽  
pp. 479-489 ◽  
Author(s):  
Thomas L. Pratt ◽  
James F. Dolan ◽  
Jackson K. Odum ◽  
William J. Stephenson ◽  
Robert A. Williams ◽  
...  
Keyword(s):  
High Resolution ◽  
Los Angeles ◽  
Hazard Assessment ◽  
Seismic Reflection ◽  
Seismic Profile ◽  
Strike Slip ◽  
Alluvial Fan ◽  
Depth Range ◽  
Seismic Reflection Profile ◽  
Santa Monica

High‐resolution seismic reflection profiles at two different scales were acquired across the transpressional Santa Monica Fault of north Los Angeles as part of an integrated hazard assessment of the fault. The seismic data confirm the location of the fault and related shallow faulting seen in a trench to deeper structures known from regional studies. The trench shows a series of near‐vertical strike‐slip faults beneath a topographic scarp inferred to be caused by thrusting on the Santa Monica fault. Analysis of the disruption of soil horizons in the trench indicates multiple earthquakes have occurred on these strike‐slip faults within the past 50 000 years, with the latest being 1000 to 3000 years ago. A 3.8-km-long, high‐resolution seismic reflection profile shows reflector truncations that constrain the shallow portion of the Santa Monica Fault (upper 300 m) to dip northward between 30° and 55°, most likely 30° to 35°, in contrast to the 60° to 70° dip interpreted for the deeper portion of the fault. Prominent, nearly continuous reflectors on the profile are interpreted to be the erosional unconformity between the 1.2 Ma and older Pico Formation and the base of alluvial fan deposits. The unconformity lies at depths of 30–60 m north of the fault and 110–130 m south of the fault, with about 100 m of vertical displacement (180 m of dip‐slip motion on a 30°–35° dipping fault) across the fault since deposition of the upper Pico Formation. The continuity of the uncomformity on the seismic profile constrains the fault to lie in a relatively narrow (50 m) zone, and to project to the surface beneath Ohio Avenue immediately south of the trench. A very high‐resolution seismic profile adjacent to the trench images reflectors in the 15 to 60 m depth range that are arched slightly by folding just north of the fault. A disrupted zone on the profile beneath the south end of the trench is interpreted as being caused by the deeper portions of the trenched strike‐slip faults where they merge with the thrust fault.

Large magnitude earthquakes of late Holocene age in the Precambrian of Finnmark, Northern Norway

2020 ◽  
Author(s):  
Odleiv Olesen ◽  
Lars Olsen ◽  
Steven Gibbons ◽  
Tormod Kværna ◽  
Bent Ole Ruud ◽  
...  
Keyword(s):  
Late Holocene ◽  
Seismic Profile ◽  
Moment Magnitude ◽  
Reverse Fault ◽  
Maximum Magnitude ◽  
Large Magnitude ◽  
Northern Norway ◽  
Seismic Profiling ◽  
Reflection Seismic ◽  
Inland Ice

<p>The 80 km long Stuoragurra postglacial fault occurs within the c. 5 km wide Precambrian Mironjavri-Sværholt Fault Zone in the northern Fennoscandian Shield. Deep seismic profiling and drilling show that the fault dips at an angle of 30-40° to the southeast. The reverse fault can be traced down to a depth of c. 2.5 km on the reflection seismic profile. A total of c. 100 earthquakes has been registered along the fault between 1991 and 2019. Recordings at the ARCES seismic array in Karasjok c. 40 km to the SE of the fault and other seismic stations in northern Norway and Finland have been utilized. The maximum moment magnitude is 4.0. The Stuoragurra fault constitutes the Norwegian part of the larger Lapland province of postglacial faults extending southwards into northern Finland and northern Sweden. The formation of these faults has previously been associated with the deglaciation of the last inland ice. Trenching of different sections of the fault and radiocarbon dating of buried and deformed organic material reveal, however, a late Holocene age (between c. 700 and 4000 years before present at three separate fault segments). The reverse displacement of c. 9 m and segment lengths of 9-12 km of the two southernmost fault segments indicate a moment magnitude of c. 7. The results from this study indicate that the maximum magnitude of future earthquakes in Fennoscandia can be significantly larger than the existing estimate of c. 6.</p>

Sand Wave Migration and its Factors on Giant Sand Ridge in Taiwan Strait

2020 ◽  
Author(s):  
Yin-Hsuan Liao ◽  
Ho-Han Hsu ◽  
Jyun-Nai Wu ◽  
Tzu-Ting Chen ◽  
Eason Yi-Cheng Yang ◽  
...  
Keyword(s):  
High Resolution ◽  
Taiwan Strait ◽  
Sand Wave ◽  
Sand Ridge ◽  
Elevation Change ◽  
Seismic Profiles ◽  
Migration Patterns ◽  
Sand Waves ◽  
And Migration ◽  
Wave Migration

<p>        Submarine sand waves are known to be induced by tidal currents and their migration has become an important issue since it may affect seafloor installations. In Taiwan Strait, widely spreading sand waves have been recognized on the Changyun Ridge, a tide-dominated giant sand ridge offshore western Taiwan. However, due to lacking of high-resolution and repeated geophysical surveys before, detailed characteristics and migrating features of the sand waves in Taiwan Strait were poorly understood. As new multibeam bathymetric and seismic data were collected repeatedly during 2016 - 2018 for offshore wind farm projects, we can now advance the understanding of sand wave characteristics and migration patterns in the study area. We apply a geostatistical analysis method on bathymetry data to reveal distribution and spatial characteristics of the sand waves, and estimate its migration pattern by using an updated spatial cross-correlation method. Then, sedimentary features, internal structures and thicknesses of sand waves are observed and estimated on high-resolution seismic profiles. Our results show that the study area is mostly superimposed by multi-scaled sandy rhythmic bed forms. However, the geomorphological and migrating characteristics of the sand waves are complicated. Their wavelengths range from 80 to 200 m, heights range from 1.5 to 8 m, and crests are generally oriented in the WNW-ESE direction. Obvious sand wave migration was detected from repeated high-resolution multi-beam data between 2016 and 2018, and migration distances can be up to ~150 m in 15 months. The average elevation change of the seafloor over the whole survey area is ~3.0 m, with a maximum value of 6.9 m. Moreover, the sand waves can migrate over 30 m with ~2.5 m elevation change in 2 months and migrate over 5 m with ~1 m elevation change in 15 days. The results also show that the orientation of wave movement can be reversed even within a small distance. By identifying the base of sand wave on seismic profiles, the thicknesses of sand waves are found ranging from 1 to 10 meters. The base of wave structure become slightly deeper from nearshore to offshore. Our results indicate that the thickness of sand waves increases with degree of asymmetry and migration rate. By bathymetric and reflection seismic data analyses, systematic spatial information of sand waves in the study area are established, and we suggest that not only tidal currents can affect sand wave migration patterns, but also wave structures and thicknesses play important roles in sand wave migrating processes and related geomorphological changes.</p>

An image of the Columbia Plateau from inversion of high‐resolution seismic data

Geophysics ◽  
1994 ◽  
Vol 59 (8) ◽  
pp. 1278-1289 ◽  
Author(s):  
William J. Lutter ◽  
Rufus D. Catchings ◽  
Craig M. Jarchow
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Velocity Structure ◽  
Interface Velocity ◽  
Seismic Profile ◽  
Fault Zones ◽  
Reliable Estimate ◽  
Low Velocity ◽  
Depth Of Penetration ◽  
Image Blurring

We use a method of traveltime inversion of high‐resolution seismic data to provide the first reliable images of internal details of the Columbia River Basalt Group (CRBG), the subsurface basalt/sediment interface, and the deeper sediment/basement interface. Velocity structure within the basalts, delineated on the order of 1 km horizontally and 0.2 km vertically, is constrained to within ±0.1 km/s for most of the seismic profile. Over 5000 observed traveltimes fit our model with an rms error of 0.018 s. The maximum depth of penetration of the basalt diving waves (truncated by underlying low‐velocity sediments) provides a reliable estimate of the depth to the base of the basalt, which agrees with well‐log measurements to within 0.05 km (165 ft). We use image blurring, calculated from the resolution matrix, to estimate the aspect ratio of imaged velocity anomaly widths to true widths for velocity features within the basalt. From our calculations of image blurring, we interpret low velocity zones (LVZ) within the basalts at Boylston Mountain and the Whiskey Dick anticline to have widths of 4.5 and 3 km, respectively, within the upper 1.5 km of the model. At greater depth, the widths of these imaged LVZs thin to approximately 2 km or less. We interpret these linear, subparallel, low‐velocity zones imaged adjacent to anticlines of the Yakima Fold Belt to be brecciated fault zones. These fault zones dip to the south at angles between 15 to 45 degrees.

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