Surface Waveform Tomography Across the Arabian-Eurasian Plate Boundary, Zagros Belt

2009 ◽  
Author(s):  
N. Shad Manaman ◽  
H. Shomali
Keyword(s):  
Plate Boundary ◽  
Eurasian Plate ◽  
Waveform Tomography

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

<p>The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10° since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.</p><p>Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V “Téthys II”, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.</p><p>The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.</p>

Evolution of migrating transform faults in anisotropic oceanic crust: examples from Iceland

2019 ◽  
Vol 56 (12) ◽  
pp. 1297-1308 ◽  
Author(s):  
Jeffrey A. Karson ◽  
Bryndís Brandsdóttir ◽  
Páll Einarsson ◽  
Kristján Sæmundsson ◽  
James A. Farrell ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Fault Zones ◽  
Plate Boundaries ◽  
Transform Fault ◽  
Eurasian Plate ◽  
Transform Faults ◽  
The North ◽  
Rift Propagation ◽  
Oriented Parallel ◽  
Ocean Ridge

Major transform fault zones link extensional segments of the North American – Eurasian plate boundary as it transects the Iceland Hotspot. Changes in plate boundary geometry, involving ridge jumps, rift propagation, and related transform fault zone migration, have occurred as the boundary has moved relative to the hotspot. Reconfiguration of transform fault zones occurred at about 6 Ma in northern Iceland and began about 3 Ma in southern Iceland. These systems show a range of different types of transform fault zones, ranging from diffuse, oblique rift zones to narrower, well-defined, transform faults oriented parallel to current plate motions. Crustal deformation structures correlate with the inferred duration and magnitude of strike-slip displacements. Collectively, the different expressions of transform zones may represent different stages of development in an evolutionary sequence that may be relevant for understanding the tectonic history of plate boundaries in Iceland as well as the structure of transform fault zones on more typical parts of the mid-ocean ridge system.

Results from geodetic measurements in the western part of the African–Eurasian plate boundary

1998 ◽  
Vol 294 (3-4) ◽  
pp. 261-269 ◽  
Author(s):  
L Bastos ◽  
J Osório ◽  
A Barbeito ◽  
G Hein
Keyword(s):  
Plate Boundary ◽  
Eurasian Plate ◽  
Geodetic Measurements

scholarly journals Large-scale slope failure and active erosion occurring in the southwest Ryukyu fore-arc area

2001 ◽  
Vol 1 (4) ◽  
pp. 203-211 ◽  
Author(s):  
T. Matsumoto ◽  
M. Kimura ◽  
M. Nakamura ◽  
T. Ono
Keyword(s):  
Large Scale ◽  
Slope Failure ◽  
Gravitational Instability ◽  
Plate Boundary ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Philippine Sea ◽  
Topographic Features ◽  
Ishigaki Island ◽  
Tensional Stress

Abstract. The southwestern Ryukyu area east of Taiwan Island is an arcuate boundary between Philippine Sea Plate and Eurasian Plate. The topographic features in the area are characterised by (1) a large-scale amphitheatre off Ishigaki Island, just on the estimated epicentre of the tsunamigenic earthquake in 1771, (2) lots of deep sea canyons located north of the amphitheatre, (3) 15–20 km wide fore-arc basin, (4) 15–20 km wide flat plane in the axial area of the trench, (5) E-W trending half grabens located on the fore-arc area, etc., which were revealed by several recent topographic survey expeditions. The diving survey by SHINKAI6500 in the fore-arc area on a spur located 120 km south of Ishigaki Island was carried out in 1992. The site is characterised dominantly by rough topography consisting of a series of steep slopes and escarpments. A part of the surface is eroded due to the weight of the sediment itself and consequently the basement layer is exposed. The site was covered with suspended particles during the diving, due to the present surface sliding and erosion. The same site was resurveyed in 1997 by ROV KAIKO, which confirmed the continuous slope failure taking place in the site. Another example that was observed by KAIKO expedition in 1997 is a largescale mud block on the southward dipping slope 80 km south of Ishigaki Island. This is apparently derived from the shallower part of the steep slope on the southern edge of the fan deposit south of Ishigaki Island. The topographic features suggest N-S or NE-SW tensional stress over the whole study area. In this sense, the relative motion between the two plates in this area is oblique to the plate boundary. So, the seaward migration of the plate boundary may occur due to the gravitational instability at the boundary of the two different lithospheric structures. This is evidenced by a lack of accretionary sediment on the fore-arc and the mechanism of a recent earthquake which occurred on 3 May 1998 in the Philippine Sea Plate 250 km SSE of Ishigaki Island.

Using 2D long-streamer seismic waveform tomography to decipher sedimentary processes surrounding a forearc fault offshore Alaska

2021 ◽  
Author(s):  
Amin Kahrizi ◽  
Matthias Delescluse ◽  
Mathieu Rodriguez ◽  
Pierre-Henri Roche ◽  
Anne Bécel ◽  
...  
Keyword(s):  
Mass Transport ◽  
Hanging Wall ◽  
Plate Boundary ◽  
Normal Fault ◽  
P Wave ◽  
Fault System ◽  
Fault Activity ◽  
Seismic Waveform ◽  
Waveform Tomography ◽  
Mass Transport Deposits

<p>Acoustic full-waveform inversion (FWI), or waveform tomography, involves use of both phase and amplitude of the recorded compressional waves to obtain a high-resolution P-wave velocity model of the propagation medium. Recent theoretical and computing advances now allow the application of this highly non-linear technique to field data. This led to common use of the FWI for industrial purposes related to reservoir imaging, physical properties of rocks, and fluid flow. Application of FWI in the academic domain has, so far, been limited, mostly because of the lack of adequate seismic data. Modern multichannel seismic (MCS) reflection data acquisition now  have long offsets which, in some cases, enable constraining FWI-derived subsurface velocities at a significant enough depth to be useful for structural or tectonic purposes.</p><p>In this study, we show how FWI can help decipher the record of a fault activity through time at the Shumagin Gap in Alaska. The MCS data were acquired on R/V Marcus G. Langseth during the 2011 ALEUT cruise using two 8-km-long seismic streamers and a 6600 cu. in. tuned airgun array. One of the most noticeable reflection features imaged on two profiles is a large, landward-dipping normal fault in the overriding plate; a structural configuration making the area prone to generating both transoceanic and local tsunamis, including from landslides. This fault dips ~40°- 45°, cuts the entire crust and connects to the plate boundary fault at ~35 km depth, near the intersection of the megathrust with the forearc mantle wedge. The fault system reaches the surface at the shelf edge 75 km from the trench and forms the ~6-km deep Sanak basin. However, the record of the recent fault activity remains unclear as contouritic currents tend to be trapped by the topography created by faults, even after they are no longer active.  Erosion surfaces and onlaps from contouritic processes as well as gravity collapses and mass transport deposits result in a complex sedimentary record that make it challenging to evaluate the fault activity using conventional MCS imaging alone. The long streamers used facilitated recording of refraction arrivals in the targeted continental slope area, which permitted running streamer traveltime tomography followed by FWI to produce coincident detailed velocity profiles to complement the reflection sections. We performed FWI imaging on two 40-km-long sections of the ALEUT lines crossing the Sanak basin. The images reveal low velocities of mass transport deposits as well as velocity inversions that may indicate mechanically weak layers linking some faults to gravity sliding on a décollement. One section also shows a velocity inversion in continuity to a bottom simulating reflector (BSR) only partially visible in the reflection image. The BSR velocity anomaly abruptly disappears across the main normal fault suggesting either an impermeable barrier or a lack of trapped fluids/gas in the hanging wall.</p>

scholarly journals Real Time Monitoring of Groundwater Fluorescence: Principle and Applicability in Nepal

2020 ◽  
Vol 15 (1) ◽  
pp. 137-143
Author(s):  
Aakriti Khadka ◽  
Christina Oikonomou ◽  
Shukra Raj Paudel
Keyword(s):  
Fluorescence Intensity ◽  
Seismic Activity ◽  
Plate Boundary ◽  
Earthquake Precursor ◽  
Natural Phenomena ◽  
Eurasian Plate ◽  
Earthquake Forecast ◽  
Fluorescent Intensity ◽  
The People ◽  
Positive Holes

 As Nepal sits on the Indo-Eurasian plate boundary, it is highly susceptible to catastrophic earthquakes which have been posing a grave threat to the people of the country. Even though earthquake is one of the most destructive natural phenomena, its occurrence is still unpredictable. Advance warning of disastrous earthquakes is crucial so that the damage due to it is minimal. Different changes in the properties of groundwater prior to earthquake have been detected which can give important hints. Among them, the increase in fluorescent intensity of groundwater comprises a significant earthquake precursor. The positive holes, formed due to tectonic stresses in rocks with peroxy defects, interact with groundwater modifying the fluorescence intensity of water. In this study, we investigate the effect of seismic activity on the groundwater fluorescence intensity. The necessity of this examination for the country is also demonstrated. Taking into account the large variation in the groundwater quality and types of rock in Nepal, the investigation of fluorescent intensity using fluorometer may unravel different uncertainties and limitations. The simplicity of fluorometer in installation, methodology, maintenance, and its sensitivity up to large catchment area make it suitable for such investigation. Till now, variations of the groundwater fluorescent intensity have not been deeply studied in Nepal. This is of high importance in terms of earthquake forecast considering the high seismic activity in Nepal which lies on a very seismically active zone.

Structural evolution and significance of a mélange in a collision belt: the Lichi Mélange and the Taiwan arc–continent collision

2001 ◽  
Vol 138 (6) ◽  
pp. 633-651 ◽  
Author(s):  
C. P. CHANG ◽  
J. ANGELIER ◽  
C. Y. HUANG ◽  
C. S. LIU
Keyword(s):  
Plate Boundary ◽  
Structural Evolution ◽  
Philippine Sea Plate ◽  
Eurasian Plate ◽  
Seismic Profiles ◽  
Forearc Basin ◽  
Weak Zone ◽  
Manila Trench ◽  
Mountain Belts ◽  
Coastal Range

The analysis of ‘mélanges’ of various types (sedimentary, diapiric, tectonic and polygenetic) is generally difficult and depends on a variety of criteria. However, understanding the nature and origin of mélanges is crucial to deciphering the evolution of some mountain belts. The Lichi Mélange of the Taiwan Coastal Range is juxtaposed against remnant forearc basin sequences by thrust faults and is composed of exotic ophiolite and sedimentary blocks, with sizes ranging from metres to kilometres, and coherent turbidite beds, all embedded in a sheared scaly argillaceous matrix. The Lichi Mélange has been interpreted either as a subduction complex, or as an olistostrome. By separating four main deformation levels based on the degree of disruption within the Lichi Mélange and adjacent sedimentary rocks, we have made new detailed geological maps and structural profiles in two key areas of the Lichi Mélange. We paid particular attention to the original stratigraphic relationships between the mélange and the adjacent flysch formation. Our field results compared with submarine seismic profiles suggest that the present-day structure of the Lichi Mélange results mainly from the shearing of lower forearc basin sequences, rather than from a subduction complex or a mere olistostrome. In Late Miocene time, because lithospheric subduction turned into arc–continent collision in the southern Taiwan area, the site of the proto-Manila trench changed from an active plate boundary into a deformation zone with several thrusts. A new plate suture zone between the Eurasian plate (eastern Central Range) and the Philippine Sea plate (Coastal Range) was therefore formed along the Longitudinal Valley. The Longitudinal Valley originated as a submarine arc–prism boundary, an innate weak zone within the overriding plate, and has become a prominent tectonic feature of the arc–continent collision. This inference is supported by observations on the Lichi Mélange in the Coastal Range and the Huatung Ridge off southeastern Taiwan.

scholarly journals Tsunami heights and limits in 1945 along the Makran coast estimated from testimony gathered 7 decades later in Gwadar, Pasni and Ormara

2021 ◽  
Vol 21 (10) ◽  
pp. 3085-3096
Author(s):  
Hira Ashfaq Lodhi ◽  
Shoaib Ahmed ◽  
Haider Hasan
Keyword(s):  
Subduction Zone ◽  
Plate Boundary ◽  
Arabian Plate ◽  
Great Earthquake ◽  
Eurasian Plate ◽  
Arrival Times ◽  
Makran Subduction Zone ◽  
Archival Documents ◽  
The Impact ◽  
The Town

Abstract. The towns of Pasni and Ormara were the most severely affected by the 1945 Makran tsunami. The water inundated land for almost 1 km at Pasni, engulfing 80 % of the huts of the town, while at Ormara the tsunami inundated land for 2.5 km, washing away 60 % of the huts. The plate boundary between the Arabian Plate and Eurasian Plate is marked by Makran subduction zone (MSZ). This Makran subduction zone in November 1945 was the source of a great earthquake (8.1 Mw) and an associated tsunami. Estimated death tolls, waves arrival times, and the extent of inundation and runup have remained vague. We summarize observations of the tsunami through newspaper items, eyewitness accounts and archival documents. The information gathered is reviewed and quantified where possible to obtain the inundation parameters specifically and understand the impact in general along the Makran coast. The quantification of runup and inundation extents is based on a field survey or old maps.

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