Orientation of broadband seismographs in the Kashmir Himalaya: Effect on vector-based studies

2021 ◽  
Author(s):  
Ramees Mir ◽  
Imtiyaz Parvez ◽  
Vinod Gaur
Keyword(s):  
Cross Correlation ◽  
High Reliability ◽  
Receiver Functions ◽  
Fast Component ◽  
P Wave ◽  
Kashmir Himalaya ◽  
Ladakh Himalaya ◽  
Moho Depths ◽  
Data Elements ◽  
Arrival Angles

<p>We used regional as well as global Rayleigh wave signals (source-receiver distance: 5°-175°; M≥ 6, Depth ≤ 150 km) recorded at 12 broadband seismic stations in northwestern Himalaya to compute arrival angles of surface waves at each station, assuming orthogonality of the horizontal components, and error-free levelling of the instrument. The average of all measurements at a station with cross-correlation values > 0.8, between Hilbert transformed vertical and radial components, was interpreted as the degree of misalignment of the horizontal components in a geographic frame of reference.</p><p>Out of the 12 station data used in this analysis, 3 were found to have instrument misorientation errors between 5° and 10° w.r.t geographic north, 2 between 10° and 15° and the remaining 7 < 5°. The number of measurements at each of these stations ranged from 75 to 331, with 11 stations having more than 90 measurements, assuring high reliability. We also analysed data from two nearby broadband instruments located in Ladakh Himalaya. One of these (LEH) with 46 measurements showed a misorientation error of 14.87°±4.87° and the other (HNL) with 48 showed an error of 0.75°±3.48°. Since misorientation errors based on less than 90 data elements are considered to be unstable, these were not used for further analysis.</p><p>We evaluated the effect of seismograph misorientations on the inverted solutions for P-wave receiver functions (RFs) and core-refracted shear waves (SKS). The errors in Moho depths and those of other intra-crustal features were within ±2 km for instrument misorientations of up to ~15°, that is close to the resolution errors. But, the SKS results, notably the azimuths of the fast component, were, found to be quite sensitive to instrument misalignment. For example, a ~14° error in orientation was found to cause a shift of up to 20° in the calculated azimuth of the fast component. Corrections of misorientation errors in both cases showed reduction of variance in the inverted solutions.</p>

scholarly journals Preliminary result for crustal properties derivation related to tectonics for hazard mitigation in Eastern Indonesia using Teleseismic P Coda

2021 ◽  
Vol 325 ◽  
pp. 01012
Author(s):  
Anang Sahroni ◽  
Leni Sophia Heliani ◽  
Cecep Pratama ◽  
Hidayat Panuntun ◽  
Wiwit Suryanto
Keyword(s):  
Cross Correlation ◽  
Receiver Functions ◽  
P Wave ◽  
Eastern Indonesia ◽  
Complex Interactions ◽  
Tectonic Processes ◽  
Resource Exploration ◽  
Crustal Origin ◽  
Different Origins ◽  
Mafic Lower Crust

Eastern Indonesia is tectonically complex, formed by different plates and microplates interactions from different origins. This complexity gives geoscientists a challenge to solve the ’jigsaw’ of the complex interactions. The understanding of tectonic processes can lead to a breakthrough in both resource exploration and disaster risk reduction. We utilize teleseismic P wave coda for random coda from scattering and deterministic coda originated from the crust-mantle boundary (Moho) to derive the crustal properties, including thickness, Vp/Vs, and qualitative scattering characteristics. For the scattering properties, we apply Iterative Cross-Correlation and Stacking (ICCS) to align the waveform. At the same time, for the crust characteristic, we employ the Receiver Functions (RF) method alongside H-k stacking. The crustal thickness recovered from the RF and H-k stacking has a good correlation with the crustal origin, where the thickness in older and stable crust originated from Sundaland and Gondwana is thicker than a younger plate of the crust arc and subduction origin. The Vp/Vs is high in a region that is interpreted to be dominated by mafic lower crust originated from oceanic-oceanic subduction during Eocene, anisotropy, or by a magmatic anomaly. The P coda also correlated well with the subsurface magmatic anomaly by providing a unique pattern.

scholarly journals Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Philipp Balling ◽  
Christoph Grützner ◽  
Bruno Tomljenović ◽  
Wim Spakman ◽  
Kamil Ustaszewski
Keyword(s):  
Balkan Peninsula ◽  
Receiver Functions ◽  
P Wave ◽  
S Wave ◽  
Slab Geometry ◽  
Surface Uplift ◽  
River Incision ◽  
Marine Terraces ◽  
Convergence System ◽  
Internal Dinarides

AbstractThe Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

scholarly journals Reliable workflow for inversion of seismic receiver function and surface wave dispersion data: a “13 BB Star” case study

2019 ◽  
Vol 24 (1) ◽  
pp. 101-120
Author(s):  
Kajetan Chrapkiewicz ◽  
Monika Wilde-Piórko ◽  
Marcin Polkowski ◽  
Marek Grad
Keyword(s):  
Surface Wave ◽  
Inverse Problems ◽  
Receiver Function ◽  
Joint Inversion ◽  
Wave Dispersion ◽  
Receiver Functions ◽  
P Wave ◽  
Surface Wave Dispersion ◽  
Phase Velocity Dispersion ◽  
Wide Range

AbstractNon-linear inverse problems arising in seismology are usually addressed either by linearization or by Monte Carlo methods. Neither approach is flawless. The former needs an accurate starting model; the latter is computationally intensive. Both require careful tuning of inversion parameters. An additional challenge is posed by joint inversion of data of different sensitivities and noise levels such as receiver functions and surface wave dispersion curves. We propose a generic workflow that combines advantages of both methods by endowing the linearized approach with an ensemble of homogeneous starting models. It successfully addresses several fundamental issues inherent in a wide range of inverse problems, such as trapping by local minima, exploitation of a priori knowledge, choice of a model depth, proper weighting of data sets characterized by different uncertainties, and credibility of final models. Some of them are tackled with the aid of novel 1D checkerboard tests—an intuitive and feasible addition to the resolution matrix. We applied our workflow to study the south-western margin of the East European Craton. Rayleigh wave phase velocity dispersion and P-wave receiver function data were gathered in the passive seismic experiment “13 BB Star” (2013–2016) in the area of the crust recognized by previous borehole and refraction surveys. Final models of S-wave velocity down to 300 km depth beneath the array are characterized by proximity in the parameter space and very good data fit. The maximum value in the mantle is higher by 0.1–0.2 km/s than reported for other cratons.

scholarly journals Crustal structure beneath Tierra del Fuego, Argentina, inferred from seismic P-wave receiver functions and ambient noise autocorrelations

2019 ◽  
Vol 751 ◽  
pp. 41-53 ◽  
Author(s):  
Carolina Buffoni ◽  
Martin Schimmel ◽  
Nora Cristina Sabbione ◽  
María Laura Rosa ◽  
Gerardo Connon
Keyword(s):  
Crustal Structure ◽  
Ambient Noise ◽  
Receiver Functions ◽  
Tierra Del Fuego ◽  
P Wave

Sharpness of the 410-km discontinuity from the P410s and P2p410s seismic phases

2019 ◽  
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Zhou Zhang ◽  
...  
Keyword(s):  
Transition Zone ◽  
Southern Africa ◽  
Amplitude Ratio ◽  
Southern China ◽  
Broad Band ◽  
Receiver Functions ◽  
P Wave ◽  
Seismic Model ◽  
Yangtze Craton ◽  
Zone Water

Summary Sharpness of the 410-km boundary is of interest because it is sensitive to water content in the transition zone. We evaluate the width of the 410-km discontinuity with a new seismic method. Our estimates are inferred from the amplitude ratio of the P2p410s and P410s seismic phases that are detected in P-wave receiver functions. We applied this method to seismic recordings from arrays of broad-band stations deployed in central Fennoscandia, southern Africa and southern China. The obtained estimates of width of the 410-km discontinuity range from 10 to 22 km and always exceed the width of 7 km which is expected for anhydrous conditions. The enlarged width may be interpreted in terms of hydrous conditions, but we have found only one region (the eastern Yangtze Craton in China) where the broad 410-km discontinuity, as expected, is accompanied by a broad transition zone. Water in the transition zone may be a kind of a global phenomenon, but evidence of the enlarged width of the transition zone may be missing in most of our data because the reference seismic model is affected by water, as well.

Moho Variations across the Northern Canadian Cordillera

2020 ◽  
Vol 91 (6) ◽  
pp. 3076-3085 ◽  
Author(s):  
Pascal Audet ◽  
Derek L. Schutt ◽  
Andrew J. Schaeffer ◽  
Clément Estève ◽  
Richard C. Aster ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
High Elevation ◽  
Receiver Functions ◽  
Moho Depth ◽  
Canadian Cordillera ◽  
Regional Seismicity ◽  
Thermal Buoyancy ◽  
Mackenzie Mountains ◽  
Moho Depths ◽  
Array Density

Abstract Moho morphology in orogens provides important constraints on the rheology and density structure of the crust and underlying mantle. Previous studies of Moho geometry in the northern Canadian Cordillera (NCC) using very sparse seismic data have indicated a flat and shallow (∼30–35  km) Moho, despite an average elevation of >1000  m above sea level attributable to increased thermal buoyancy and lower crustal flow due to elevated temperatures. We estimate Moho depth using receiver functions from an expanded dataset incorporating 173 past and recently deployed broadband seismic stations, including the EarthScope Transportable Array, Mackenzie Mountains transect, and other recent deployments. We determine Moho depths in the range 27–43 km, with mean and standard deviations of 33.0 and 3.0 km, respectively, and note thickened crust beneath high-elevation seismogenic regions. In the Mackenzie Mountains, thicker crust is interpreted as due to crustal stacking from thrust sheet emplacement. The edge of this region of thickened crust is interpreted to delineate the extent of the former Laurentian margin beneath the NCC and is associated with a transition from thrust to strike-slip faulting observed in regional seismicity. More geographically extensive seismograph deployments at EarthScope Transportable Array density and scale will be required to further extend crustal-scale and lithosphere-scale imaging in western Canada.

Automatic detection and picking of P-wave arrival in locally stationary noise using cross-correlation

2014 ◽  
Vol 26 ◽  
pp. 87-100 ◽  
Author(s):  
El Hassan Ait Laasri ◽  
Es-Saïd Akhouayri ◽  
Dris Agliz ◽  
Abderrahman Atmani
Keyword(s):  
Cross Correlation ◽  
Automatic Detection ◽  
P Wave ◽  
Stationary Noise ◽  
Wave Arrival

scholarly journals Seismic Structure Beneath the Wellington Region from Receiver Functions

2021 ◽  
Author(s):  
◽  
Lucy Caroline Hall
Keyword(s):  
New Zealand ◽  
Seismic Data ◽  
Seismic Velocity ◽  
Receiver Functions ◽  
P Wave ◽  
The West ◽  
Seismic Stations ◽  
Short Period ◽  
The Individual ◽  
Velocity Layer

<p>Seismic velocity structures, interpreted as being associated with the Hikurangi subduction system beneath the lower North Island of New Zealand, are imaged using stacked P wave receiver functions computed using teleseismic earthquakes. Receiver functions are a seismological technique that exploits the phenomenon of wave conversion. The upcoming P wave interacts with seismic velocity impedance contrasts below the receiving station to produce polarized P to SV converted phases. The time delay between the first arriving P wave and the SV converted phase is interpreted to infer the depth of interfaces and the velocity structure directly below the receiver, allowing estimates to be made of the physical properties of the interface. Passive seismic data were recorded at eighteen seismic stations deployed across a ~90km transect stretching across the breadth of lower North Island of New Zealand, from Kapiti Island, 5km off the west coast, to the eastern coast. The transect is oriented normal to the strike of the subducting Pacific Plate, as it dives beneath the overriding Australian Plate. Data were recorded at 10 broadband and 2 short period sensors, deployed as part of the Seismic Array Hikurangi Project (SAHKE 1 deployment), 3 Geonet (New Zealand Geonet Project) permanent short period stations, and 3 temporary stations from part of the 1991-1992 POMS project. Seismic data were recorded between November 2009 and March 2010 on the short period sensors and up to 18 months on the broadband sensor. Data recorded between November 2009 and November 2011 were utilised from the Geonet stations. P wave receiver functions are computed using the multi-taper correlation method using 389 > 6.0 Mw teleseismic earthquakes recorded at the individual seismic stations. A total of 1082 individual receiver functions from all the stations are stacked for both the individual stations and as a ‘super-stack’ across the complete transect, using the common conversion point (CCP) method. The CCP stack shows a distinct, thick low velocity layer (LVL), dipping to the west, from ~18km depth in the east to ~30km depth in the west. This is above a higher velocity layer, also dipping west, at depths of between ~22km and ~ 37km. The LVL is interpreted as being subducted sediments overlying the higher velocity plate interface. Structures towards the west indicate the presence of possibly imbricated features associated with the overriding plate. Deeper structures, down to a depth of 140km are evident, but have less clarity than the shallower features. Some of the deeper layers appear to be dipping towards the west, some to the east. The results of the CCP stack agree well with results from active source methods.</p>

Sign in / Sign up

Export Citation Format

Share Document