Upper-plate structure in Ecuador coincident with the subduction of the Carnegie Ridge and the southern extent of large mega-thrust earthquakes

SUMMARY The Ecuadorian convergent margin has experienced many large mega-thrust earthquakes in the past century, beginning with a 1906 event that propagated along as much as 500 km of the plate interface. Many subsections of the 1906 rupture area have subsequently produced Mw ≥ 7.7 events, culminating in the 16 April 2016, Mw 7.8 Pedernales earthquake. Interestingly, no large historic events Mw ≥ 7.7 appear to have propagated southward of ∼1°S, which coincides with the subduction of the Carnegie Ridge. We combine data from temporary seismic stations deployed following the Pedernales earthquake with data recorded by the permanent stations of the Ecuadorian national seismic network to discern the velocity structure of the Ecuadorian forearc and Cordillera using ambient noise tomography. Ambient noise tomography extracts Vsv information from the ambient noise wavefield and provides detailed constraints on velocity structures in the crust and upper mantle. In the upper 10 km of the Ecuadorian forearc, we see evidence of the deepest portions of the sedimentary basins in the region, the Progreso and Manabí basins. At depths below 30 km, we observe a sharp delineation between accreted fast forearc terranes and the thick crust of the Ecuadorian Andes. At depths ∼20 km, we see a strong fast velocity anomaly that coincides with the subducting Carnegie Ridge as well as the southern boundary of large mega-thrust earthquakes. Our observations raise the possibility that upper-plate structure, in addition to the subducting Carnegie Ridge, plays a role in the large event segmentation seen along the Ecuadorian margin.

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Lithospheric structure of the Pannonian Basin using Rayleigh wave ambient noise tomography – preliminary results

10.5194/egusphere-egu2020-10726 ◽

2020 ◽

Author(s):

Máté Timkó ◽

Lars Wiesenberg ◽

Amr El-Sharkawy ◽

Zoltán Wéber ◽

Thomas Meier ◽

...

Keyword(s):

Phase Velocity ◽

Rayleigh Wave ◽

Ambient Noise ◽

Velocity Structure ◽

Pannonian Basin ◽

Vertical Component ◽

Ambient Noise Tomography ◽

Crust And Upper Mantle ◽

Mountain Chain ◽

One Year

We used Rayleigh wave ambient noise tomography to investigate the crust and uppermost mantle structure of the Pannonian Basin. The Pannonian Basin and the surrounding orogens are located within the arcuate Alpine&#8211;Carpathian mountain chain in Central Europe. It is a back-arc basin characterized by a thinned lower crust and an updoming mantle. Benath the basin both the crust and the lithosphere have smaller thickness than the continental average. Imaging the velocity structure of the crust and upper mantle may help us to better understand the structure and formation of the Carpathian&#8211;Pannonian region.We used data from the permanent seismological stations of the broader Central European region together with the AlpArray Seismic Network (AASN) and analysed one-year seismic data from 2017. More than 18 thousand vertical component noise cross-correlation functions were calculated and Rayleigh wave inter-station phase velocity curves were determined using an automated measuring algorithm. Anisotropic phase velocity tomographic imaging were carried out for the whole Pannonian Basin between 2 and 40s periods (~5-60 km).The locations of the retrieved phase-velocity anomalies consistent with the well-known geologic and tectonic structure of the area (deep basins and orogenic belts) and are comparable to recent tomographic models published in the literature.

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Imaging the shallow crustal velocity structure of the Qingchengzi ore field on the Liaodong Peninsula, China, with a short-period dense array using ambient noise tomography

Tectonophysics ◽

10.1016/j.tecto.2021.228913 ◽

2021 ◽

pp. 228913

Author(s):

Tongtong Xie ◽

Tao Xu ◽

Yinshuang Ai ◽

Qingdong Zeng ◽

Wei Zhang ◽

...

Keyword(s):

Ambient Noise ◽

Velocity Structure ◽

Dense Array ◽

Ambient Noise Tomography ◽

Crustal Velocity ◽

Crustal Velocity Structure ◽

Short Period ◽

Liaodong Peninsula

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Ambient noise tomography of three-dimensional near-surface shear-wave velocity structure around the hydraulic fracturing site using surface microseismic monitoring array

Journal of Applied Geophysics ◽

10.1016/j.jappgeo.2018.08.009 ◽

2018 ◽

Vol 159 ◽

pp. 209-217 ◽

Cited By ~ 4

Author(s):

Ying Liu ◽

Haijiang Zhang ◽

Hongjian Fang ◽

Huajian Yao ◽

Ji Gao

Keyword(s):

Shear Wave Velocity ◽

Ambient Noise ◽

Velocity Structure ◽

Three Dimensional ◽

Microseismic Monitoring ◽

Ambient Noise Tomography ◽

Surface Shear ◽

Near Surface ◽

Surface Shear Wave ◽

Shear Wave Velocity Structure

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The Australian Plate and underlying mantle from waveform tomography with massive datasets

10.5194/egusphere-egu21-5272 ◽

2021 ◽

Author(s):

Janneke de Laat ◽

Sergei Lebedev ◽

Bruna Chagas de Melo ◽

Nicolas Celli ◽

Raffaele Bonadio

Keyword(s):

Structural Information ◽

Azimuthal Anisotropy ◽

P Wave ◽

Depth Range ◽

S Wave ◽

Crust And Upper Mantle ◽

Southern Boundary ◽

Velocity Anomaly ◽

Australian Plate ◽

Australian Continent

We present a new S-wave velocity tomographic model of the Australian Plate, Aus21.&#160; It is constrained by waveforms of 0.9 million seismograms with both the corresponding sources and stations located within the half-hemisphere centred at the Australian continent. Waveform inversion extracts structural information from surface, S- and multiple S-waves on the seismograms in the form of a set of linear equations. These equations are then combined in a large linear system and inverted jointly to obtain a tomographic model of S- and P-wave speeds and S-wave azimuthal anisotropy of the crust and upper mantle. The model has been validated by resolution tests and, for particular locations in Australia with notable differences with previous models, by independent inter-station measurements of surface-wave phase velocities, which we performed using available array data.&#160;&#160;Aus21 offers new insights into the structure and evolution of the Australian Plate and its boundaries. The Australian cratonic lithosphere occupies nearly all of the western and central Australia but shows substantial lateral heterogeneity. It extends up to the northern edge of the plate, where it is colliding with island arcs, without subducting. The rugged eastern boundary of the cratonic lithosphere provides a lithospheric definition of the Tasman Line. The thin, warm lithosphere below the eastern part of the continent, east of the Tasman Line, underlies the Cenozoic volcanism locations in the area. The lithosphere is also thin and warm below much of the Tasman Sea, underlying the Lord Howe hotspot and the submerged part of western Zealandia. A low velocity anomaly that may indicate the single source of the Lord Howe and Tasmanid hotspots is observed in the transition zone offshore the Australian continent, possibly also sourcing the East Australia hotspot. Another potential hotspot source is identified below the Kermadec Trench, causing an apparent slab gap in the overlying slab and possibly related to the Samoa Hotspot to the north. Below a portion of the South East Indian Ridge (the southern boundary of the Australian Plate) a pronounced high velocity anomaly is present in the 200-400 km depth range just east of the Australian-Antarctic Discordance (AAD), probably linked to the evolution of this chaotic ridge system.

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Crustal and upper mantle velocity structure of the Pannonian Region using Rayleigh wave ambient noise tomography

10.5194/egusphere-egu21-14525 ◽

2021 ◽

Author(s):

Máté Timkó ◽

Lars Wiesenberg ◽

Amr El-Sharkawy ◽

Zoltán Wéber ◽

Thomas Meier ◽

...

Keyword(s):

Rayleigh Wave ◽

Ambient Noise ◽

Velocity Structure ◽

Pannonian Basin ◽

Vertical Component ◽

High Heat ◽

Moho Depth ◽

Ambient Noise Tomography ◽

Period Range ◽

Waveform Data

The Pannonian Basin is located in Central-Europe surrounded by the Alpine, Carpathian, and Dinarides mountain ranges. This is a back-arc basin characterized by shallow Moho depth, updoming mantle and high heat flow. In this study, we present the results of the Rayleigh wave based ambient noise tomography to investigate the velocity structure of the Carpathian-Pannonian region.&#160;For the ambient noise measurements, we collected the continuous waveform data from more than 1280 seismological stations from the broader Central-Eastern European region. This dataset embraces all the permanent and the temporary (AlpArray, PASSEQ, CBP, SCP) stations from the 9-degree radius of the Pannonian Basin which were operating between the time period between 2005 and 2018. All the possible vertical component noise cross-correlation functions were calculated and all phase velocity curves were determined in the 5-80 s period range using an automated measuring algorithm.&#160;The collected dispersion measurements were then used to create tomographic images that are characterized by similar velocity anomalies in amplitude, pattern and location that are consistent with the well-known tectonic and geologic structure of the research area and are comparable to previous tomographic models published in the literature.

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Near-surface Structure of Downtown Jinan, China: Application of Ambient Noise Tomography with a Dense Seismic Array

Journal of Environmental and Engineering Geophysics ◽

10.2113/jeeg24.4.641 ◽

2019 ◽

Vol 24 (4) ◽

pp. 641-652

Author(s):

Feng Liang ◽

Zhihui Wang ◽

Hailong Li ◽

Kai Liu ◽

Tao Wang

Keyword(s):

Surface Wave ◽

Human Activities ◽

High Frequency ◽

Urban Areas ◽

Ambient Noise ◽

Velocity Structure ◽

Shear Velocity ◽

Ambient Noise Tomography ◽

Surface Wave Dispersion ◽

Near Surface

Urban geophysics ups the ante in the world of applied geophysics, which requires innovative thinking and seemingly off-the-wall approaches, if for no other reason than the settings. Ambient-noise-tomography (ANT) can play a pivotal role in yielding subsurfa2ce information in urban areas, which is capable of dealing with challenges related to these scenarios ( e.g., human activities and low signal-to-noise ratio). In this study, the ANT was conducted to investigate the near-surface shear-velocity structure in the surrounding area of the Baotu Spring Park in downtown Jinan, Shandong Province, China. Quiet clear Rayleigh waves have been obtained by the cross-correlation, which indicates that strong human activities, such as moving vehicles and municipal engineering constructions, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surface-wave tomographic method with period-dependent ray-tracing was used to invert all surface-wave dispersion data in the period band 0.2-1.5 s simultaneously for 3D variations of shear-velocity (Vs) structure. Our results show a good correspondence to the geological features with thinner Quaternary sediments, the geological structural characteristic of the limestone surrounded by the igneous which has the highest velocity than that of the limestone in the study area, and several concealed faults of which specific location has been detected at depth. The results demonstrate that it is possible to successfully use ANT with high-frequency signal in an urban environment provided a detailed planning and execution is implemented.

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An improved velocity model for the crust and upper mantle along the central mobile belt of the Newfoundland Appalachian orogen and its offshore extension

Canadian Journal of Earth Sciences ◽

10.1139/e98-042 ◽

1998 ◽

Vol 35 (11) ◽

pp. 1238-1251 ◽

Cited By ~ 5

Author(s):

Deping Chian ◽

François Marillier ◽

Jeremy Hall ◽

Garry Quinlan

Keyword(s):

Upper Mantle ◽

Lower Crust ◽

Velocity Structure ◽

Sedimentary Basins ◽

Velocity Model ◽

Mobile Belt ◽

Wide Angle ◽

Crust And Upper Mantle ◽

Angle Data ◽

Appalachian Orogen

New modelling of wide-angle reflection-refraction data of the Canadian Lithoprobe East profile 91-1 along the central mobile belt of the Newfoundland Appalachian orogen reveals new features of the upper mantle, and establishes links in the crust and upper mantle between existing land and marine wide-angle data sets by combining onshore-offshore recordings. The revised model provides detailed velocity structure in the 30-34 km thick crust and the top 30 km of upper mantle. The lower crust is characterized by a velocity of 6.6-6.8 km/s onshore, increasing by 0.2 km/s to the northeast offshore beneath the sedimentary basins. This seaward increase in velocity may be caused by intrusion of about 4 km of basic rocks into the lower crust during the extension that formed the overlying Carboniferous basins. The Moho is found at 34 km depth onshore, rising to 30 km offshore to the northeast with a local minimum of 27 km. The data confirm the absence of deep crustal roots under the central mobile belt of Newfoundland. Our long-range (up to 450 km offset) wide-angle data define a bulk velocity of 8.1-8.3 km/s within the upper 20 km of mantle. The data also contain strong reflective phases that can be correlated with two prominent mantle reflectors. The upper reflector is found at 50 km depth under central Newfoundland, rising abruptly towards the northeast where it reaches a minimum depth of 36 km. This reflector is associated with a thin layer (1-2 km) unlikely to coincide with a discontinuity with a large cross-boundary change in velocity. The lower reflector at 55-65 km depths is much stronger, and may have similar origins to reflections observed below the Appalachians in the Canadian Maritimes which are associated with a velocity increase to 8.5 km/s. Our data are insufficient for discriminating among various interpretations for the origins of these mantle reflectors.

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