scholarly journals Analisa Receiver Function Teleseismic untuk Mendeteksi Moho pada Stasiun Bkb Data Meramex

2016 ◽  
Vol 3 (02) ◽  
pp. 195 ◽  
Author(s):  
Rian Amukti ◽  
Wiwit Suryanto
Keyword(s):  
Transition Zone ◽  
Lower Crust ◽  
Bandpass Filter ◽  
Receiver Function ◽  
Velocity Model ◽  
Upper Crust ◽  
Experiment Data ◽  
Broadband Seismometer ◽  
Crustal Model ◽  
Teleseismic Event

<span>It has been done a research to determine internal earth using receiver function teleseismic analysis <span>method. This method have been done by using MERAMEX (MErapi Amphibious Experiment) data from <span>broadband seismometer BKB. Event of teleseismic is chosen from Honshu Japan with radius 30<span>o <span>and <span>magnitude 7.2. This research begun by analysing radial and vertical characteristic of teleseismic event<br /><span>and using bandpass filter with range 0.003 Hz – 0.5 Hz. Then Iteractive Deconvolution is used to get <span>velocity model. The result of this model shows crustal model that has 4 Km thick upper crust, a 26 Km <span>thick lower crust and 10 Km thick Moho transition zone, with velocity increasing gradually.</span></span></span></span></span></span><br /></span></span></span>

Anomalously deep earthquakes in the March 2018 swarm along the Western Margin of Afar

2020 ◽  
Author(s):  
Alessandro La Rosa ◽  
Cecile Doubre ◽  
Carolina Pagli ◽  
Federico Sani ◽  
Giacomo Corti ◽  
...  
Keyword(s):  
Lower Crust ◽  
Surface Deformation ◽  
Receiver Function ◽  
Velocity Model ◽  
Normal Faults ◽  
Active System ◽  
Western Margin ◽  
Afar Depression ◽  
Crustal Earthquakes ◽  
Using Data

&lt;p&gt;During the evolution of continental rift systems, extension focuses along on-axis magmatic segments while extensional structures along the rift margins seem to progressively become inactive. However, how strain is partitioned between rift axes and rift margins is still poorly understood. The Afar Rift is the locus of extension between Nubia, Arabia and Somalia and is believed to record the latest stages of rifting and incipient continental break-up. The Afar rift axis is bounded at its western margin by a seismically active system of normal faults separating the Afar depression from the Ethiopian Plateau through a series of large bounding faults and marginal grabens. Although most of the extension in Afar is currently accommodated on-axis, several earthquakes with Mw &gt; 5.0 occurred in the past decades on the Western Afar Margin (WAM). Here we analysed the most recent M&lt;sub&gt;w&lt;/sub&gt; 5.2 earthquake on the WAM on 24 March 2018 and the following seismic sequence using data recorded by a temporary seismic network, set up between 2017 and 2018. We located 800 events from the 20 March to the 30 April 2018 using twenty-three local seismic stations and a new velocity model for the WAM based on a new receiver function study. Preliminary results show that seismicity during the 2018 event focused at mid-to-low crustal depths (from ~15 km to ~35 km) along west-dipping fault planes. Shallower upper crustal earthquakes also occurred on west-dipping fault planes.&lt;/p&gt;&lt;p&gt;The hypocentral location of the mainshock has also been investigated using InSAR. We processed four independent interferograms using Sentinel-1 data acquired from a descending track. None of them shows any significant surface deformation, confirming the large depth of the hypocenters. Furthermore, we tested possible ranges of depth by producing a series of forward models assuming fault located at progressively increasing depths and corresponding to a Mw 5.2 earthquake. Our models show that surface deformations are &lt; 1 cm at depths greater than 15 km, in agreement with our hypocentral depth of 18 km for the main shock estimated from seismic data.&amp;#160;&lt;/p&gt;&lt;p&gt;Our seismicity observations of slip along west-dipping faults show that deformation across the WAM is currently accommodated by antithetic faulting, as suggested by structural geology studies. Lower crustal earthquakes might occur in a strong lower crust due to the presence of mafic lower crust and/or be induced by migrating fluids such as magma or CO&lt;sup&gt;2&lt;/sup&gt;.&lt;/p&gt;

Multilayered Crustal Anisotropy in Eastern Tibet Revealed by Receiver Function Data

2020 ◽  
Author(s):  
Shaohua Qi ◽  
Qiyuan Liu ◽  
Jiuhui Chen ◽  
Biao Guo
Keyword(s):  
Tibetan Plateau ◽  
Lower Crust ◽  
Seismic Anisotropy ◽  
Receiver Function ◽  
Azimuthal Anisotropy ◽  
Strain History ◽  
The Tibetan Plateau ◽  
Anisotropy Axis ◽  
Upper Crust ◽  
Western Sichuan

&lt;p&gt;It is widely accepted that the ongoing India-Asia collision since approximately 50 Ma ago has resulted in the uplift and eastward expansion of the Tibetan Plateau. Yet the interpretations of its dynamic process and deformation mechanism still remain controversial. Distinct models that emphasize particular aspects of the tectonic features have been proposed, including fault-controlled rigid blocks, continuous deformation of lithosphere and lower crust flow.&lt;/p&gt;&lt;p&gt;One possible way to reconcile these models is to investigate crustal deformation at multiple depths simultaneously, as well as crust-mantle interaction. Seismic anisotropy is considered as an effective tool to study the geometry and distribution of subsurface deformation, due to its direct connection to the stress state and strain history of anisotropic structures and fabrics. In the eastern margin of Tibetan plateau, previous studies of seismic anisotropy have already provided useful insights into the bulk anisotropic properties of the entire crust or upper mantle, based on shear wave splitting analyses of Moho Ps and XKS phases.&lt;/p&gt;&lt;p&gt;In this study, we went further to extract anisotropic parameters of multiple crustal layers by waveform inversion of teleseismic receiver function (RF) data from the western-Sichuan temporal seismic array using particle swarm optimization. Instead of directly fitting the backazimuthal stacking of RFs from each station, we translated the RF data into backazimuthal harmonic coefficients using harmonic decomposition technique, which separates the signals (of planar isotropic structure and anisotropy) from the scattering noise generated by non-planar lateral heterogeneity. The constant (k=0) and k=1, 2 terms of backazimuthal harmonic coefficients were used in our inversion. We also fixed the anisotropic model to slow-axis symmetry to avoid ambiguous interpretations.&lt;/p&gt;&lt;p&gt;Our results show that:&lt;/p&gt;&lt;p&gt;(1) Anisotropy with a titled anisotropy axis of symmetry is more commonly observed than pure azimuthal anisotropy in our data, which has been also reported by other RF studies across the surrounding areas of Tibetan plateau.&lt;/p&gt;&lt;p&gt;(2) The trends of slow symmetry axis vary from the upper to lower part of the crust in both Chuandian and Songpan units, indicating the deformation of the upper crust is decoupled from that of the lower crust in these two regions, while the trends are more consistent throughout the crust in the Sichuan basin.&lt;/p&gt;&lt;p&gt;(3) In the upper crust, the trends show a degree of tendency to lie parallel to the major geological features such as the Xianshuihe and Longmenshan faults, exhibiting a fault-controlled deformation or movement. In the middle and lower crust, the trends are NS or NW-SE in Chuandian unit and NE-SW in Songpan unit, which are coincident with the apparent extension directions of the ductile crustal flow.&lt;/p&gt;

scholarly journals Common reflection point mapping of the mantle transition zone using recorded and 3-D synthetic ScS reverberations

2019 ◽  
Vol 220 (1) ◽  
pp. 724-736
Author(s):  
Samuel M Haugland ◽  
Jeroen Ritsema ◽  
Daoyuan Sun ◽  
Jeannot Trampert ◽  
Maria Koroni
Keyword(s):  
Transition Zone ◽  
Large Scale ◽  
Receiver Function ◽  
Wave Theory ◽  
Shear Velocity ◽  
Velocity Model ◽  
Reflection Point ◽  
Mantle Transition Zone ◽  
Point Mapping ◽  
Continental Scale

SUMMARY The method of ScS reverberation migration is based on a ‘common reflection point’ analysis of multiple ScS reflections in the mantle transition zone (MTZ). We examine whether ray-theoretical traveltimes, slownesses and reflection points are sufficiently accurate for estimating the thickness H of the MTZ, defined by the distance between the 410- and 660-km phase transitions. First, we analyse ScS reverberations generated by 35 earthquakes and recorded at hundreds of seismic stations from the combined Arrays in China, Hi-NET in Japan and the Global Seismic Network. This analysis suggests that H varies by about 30 km and therefore that dynamic processes have modified the large-scale structure of the MTZ in eastern Asia and the western Pacific region. Second, we apply the same procedure to spectral-element synthetics for PREM and two 3-D models. One 3-D model incorporates degree-20 topography on the 410 and 660 discontinuities, otherwise preserving the PREM velocity model. The other model incorporates the degree-20 velocity heterogeneity of S20RTS and leaves the 410 and 660 flat. To optimize reflection point coverage, our synthetics were computed assuming a homogeneous grid of stations using 16 events, four of which are fictional. The resolved image using PREM synthetics resembles the PREM structure and indicates that the migration approach is correct. However, ScS reverberations are not as strongly sensitive to H as predicted ray-theoretically because the migration of synthetics for a model with degree-20 topography on the 410 and 660: H varies by less than 5 km in the resolved image but 10 km in the original model. In addition, the relatively strong influence of whole-mantle shear-velocity heterogeneity is evident from the migration of synthetics for the S20RTS velocity model and the broad sensitivity kernels of ScS reverberations at a period of 15 s. A ray-theoretical approach to modelling long-period ScS traveltimes appears inaccurate, at least for continental-scale regions with relatively sparse earthquake coverage. Additional modelling and comparisons with SS precursor and receiver function results should rely on 3-D waveform simulations for a variety of structures and ultimately the implementation of full wave theory.

Receiver Function mapping of mantle transition zone discontinuities beneath Western Alps using scaled 3-D velocity corrections

2021 ◽  
Author(s):  
Dongyang Liu ◽  
Liang Zhao ◽  
Anne Paul ◽  
Huaiyu Yuan ◽  
Stefano Solarino ◽  
...  
Keyword(s):  
Transition Zone ◽  
Receiver Function ◽  
Velocity Model ◽  
Western Alps ◽  
Orogenic Belt ◽  
P Wave ◽  
Mantle Transition Zone ◽  
3D Velocity Model ◽  
The Alps ◽  
European Plate

&lt;p&gt;The Alpine orogenic belt is the result of the continental collision and convergence&amp;#160;between the Adriatic microplate and European plate&amp;#160;during the Mesozoic.&amp;#160;The Alps orogenic belt has a complex tectonic history and the deformation in and around the Alps are significantly affected by several microplates (e.g., Adriatic and Iberia)&amp;#160;and&amp;#160;blocks,&amp;#160;in particular the Apennines, Betics, Dinarides. The mantle transition zone is delineated by seismic velocity discontinuities around the depths of 410 and 660 km&amp;#160;which are generally interpreted as polymorphic phase changes in the olivine system and garnet-pyroxene system.The subduction depth of the European plate and the origin of the mantle flow behind the plate plays crucial roles for our understanding of regional geodynamic (Zhao et al., 2016; Hua et al.,&amp;#160;2017).&amp;#160;Therefore, we use&amp;#160;receiver function&amp;#160;method to study the seismic features of discontinuities beneath&amp;#160;the Western Alps&amp;#160;to constrain the structure of subducted plate and study the geodynamic origin of the low velocity anomaly behind the subduction zone and its relationship with the high-relief&amp;#160;topography.&amp;#160;&lt;/p&gt;&lt;p&gt;This study uses data collected from 293 permanent and temporary broadband seismic stations (e.g., CIFALPS). Teleseismic events are selected from 30&lt;sup&gt;o&lt;/sup&gt;&amp;#160;to 90&lt;sup&gt;o &lt;/sup&gt;epicentral distrance with magnitudes (Mw) between 5.3 and 9.0. Data are carefully checked&amp;#160;by automated&amp;#160;and manual&amp;#160;procedures to to give a total of 24904&amp;#160;receiver functions. Both 1D velocity model of the IASP91 and 3D velocity model of the EU60 (Zhu et al., 2015) are used for time-to-depth migration. The results show that&amp;#160;using 3D velocity model to image the two discontinuities may obtain a more accurate structure image of the mantle transition zone.&lt;/p&gt;&lt;p&gt;In the northern part of the study area, along the alpine orogenic belt, we find a localized arc-shaped thinning area&amp;#160;with a depressed&amp;#160;410 discontinuity, which is attributed to hot mantle upwellings.&amp;#160;The uplift&amp;#160;is&amp;#160;hardly&amp;#160;seen on the 660 discontinuity, suggesting that&amp;#160;the thermal anomaly is unlikely to be interpreted as a mantle plume. The uplift of the 410-km can be interpreted as the European plate subducting to the depth of the upper transition zone. The depression of the 660-km &amp;#160;is likely attributed&amp;#160;to the remnants from the oceanic mantle lithosphere that detached from the Eurasian plate after closure of the Alpine Tethys.&amp;#160;Our results show&amp;#160;a good agreement&amp;#160;between the thinning area of MTZ and the area of topographic uplift, the mantle upwelling promotes the temperature increase which is conducive to the uplift of topographic.&lt;/p&gt;&lt;p&gt;Reference&lt;/p&gt;&lt;p&gt;Zhao L , Paul A , Marco G. Malus&amp;#224;, et al. Continuity of the Alpine slab unraveled by high-resolution P-wave tomography. Journal of Geophysical Research: Solid Earth, 2016, 121.&lt;/p&gt;&lt;p&gt;Hua, Y., D. Zhao, and Y. Xu (2017), P wave anisotropic tomography of the Alps, J. Geophys. Res. Solid Earth, 122, 4509&amp;#8211;4528, doi:10.1002/2016JB013831.&lt;/p&gt;&lt;p&gt;Zhu H,Bozdag E and Tromp J.Seismic structure of the European upper mantle based on adjoint tomography.Geophys. J. Int. 2015, 201, 18&amp;#8211;52&lt;/p&gt;

Results of a seismic reflection survey across the fault zone between the Thompson nickel belt and the Churchill Tectonic Province, northern Manitoba

1981 ◽  
Vol 18 (1) ◽  
pp. 13-25 ◽  
Author(s):  
A. G. Green
Keyword(s):  
Fault Zone ◽  
Lower Crust ◽  
Seismic Reflection ◽  
High Amplitude ◽  
Small Scale ◽  
Upper Crust ◽  
Travel Times ◽  
Reflection Point ◽  
Point Data ◽  
Amplitude Reflection

Approximately 11 km of four-fold common reflection point data have been recorded across a region that spans the contact fault zone between the Thompson nickel belt and the Churchill Tectonic Province. From these data it is shown that the upper crust in this region and, to a lesser extent, the lower crust are characterized by numerous scattered events that originate from relatively small-scale features. Within the Thompson nickel belt two extensive and particularly high-amplitude reflection zones, at two-way travel times of t = 5.0–5.5 s and t = 6.0–6.5 s, are recorded with apparent northwesterly dips of 0–20 °C. These reflection zones, which have a laminated character, are truncated close to the faulted contact with the Churchill Province. Both the contact fault zone and the Churchill Province in this region have crustal sections that are relatively devoid of significant reflectors. The evidence presented here confirms that the crustal section of the Thompson nickel belt is fundamentally different from that of the Churchill Tectonic Province.

Dynamics of the extension in the Fonualei Rift in the northern Lau Basin at 16 °S

2021 ◽  
Author(s):  
Anna Jegen ◽  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Udo Barckhausen ◽  
Ingo Heyde ◽  
...  
Keyword(s):  
Velocity Gradient ◽  
Lower Crust ◽  
Pacific Plate ◽  
P Wave ◽  
Upper Crust ◽  
Lau Basin ◽  
Australian Plate ◽  
The Pacific ◽  
Refraction Seismic ◽  
Roll Back

&lt;p&gt;The Lau Basin is a young back-arc basin steadily forming at the Indo-Australian-Pacific plate boundary, where the Pacific plate is subducting underneath the Australian plate along the Tonga-Kermadec island arc. Roughly 25 Ma ago, roll-back of the Kermadec-Tonga subduction zone commenced, which lead to break up of the overriding plate and thus the formation of the western Lau Ridge and the eastern Tonga Ridge separated by the emerging Lau Basin.&lt;/p&gt;&lt;p&gt;As an analogue to the asymmetric roll back of the Pacific plate, the divergence rates decline southwards hence dictating an asymmetric, V-shaped basin opening. Further, the decentralisation of the extensional motion over 11 distinct spreading centres and zones of active rifting has led to the formation of a composite crust formed of a microplate mosaic. A simplified three plate model of the Lau Basin comprises the Tonga plate, the Australian plate and the Niuafo'ou microplate. The northeastern boundary of the Niuafo'ou microplate is given by two overlapping spreading centres (OLSC), the southern tip of the eastern axis of the Mangatolu Triple Junction (MTJ-S) and the northern tip of the Fonualei Rift spreading centre (FRSC) on the eastern side. Slow to ultraslow divergence rates were identified along the FRSC (8-32 mm/a) and slow divergence at the MTJ (27-32 mm/a), both decreasing southwards. However, the manner of divergence has not yet been identified. Additional regional geophysical data are necessary to overcome this gap of knowledge.&lt;/p&gt;&lt;p&gt;Research vessel RV Sonne (cruise SO267) set out to conduct seismic refraction and wide-angle reflection data along a 185 km long transect crossing the Lau Basin at ~16 &amp;#176;S from the Tonga arc in the east, the overlapping spreading centres, FRSC1 and MTJ-S2, and extending as far as a volcanic ridge in the west. The refraction seismic profile consisted of 30 ocean bottom seismometers. Additionally, 2D MCS reflection seismic data as well as magnetic and gravimetric data were acquired.&lt;/p&gt;&lt;p&gt;The results of our P-wave traveltime tomography show a crust that varies between 4.5-6 km in thickness. Underneath the OLSC the upper crust is 2-2.5 km thick and the lower crust 2-2.5 km thick. The velocity gradients of the upper and lower crust differ significantly from tomographic models of magmatically dominated oceanic ridges. Compared to such magmatically dominated ridges, our final P-wave velocity model displays a decreased velocity gradient in the upper crust and an increased velocity gradient in the lower crust more comparable to tectonically dominated rifts with a sparse magmatic budget.&lt;/p&gt;&lt;p&gt;The dominance of crustal stretching in the regional rifting process leads to a tectonical stretching, thus thinning of the crust under the OLSC and therefore increasing the lower crust&amp;#8217;s velocity gradient. Due to the limited magmatic budget of the area, neither the magnetic anomaly nor the gravity data indicate a magmatically dominated spreading centre. We conclude that extension in the Lau Basin at the OLSC at 16 &amp;#176;S is dominated by extensional processes with little magmatism, which is supported by the distribution of seismic events concentrated at the northern tip of the FRSC.&lt;/p&gt;

Reconnaissance seismic refraction-reflection surveys in northwestern New Mexico

1984 ◽  
Vol 74 (4) ◽  
pp. 1263-1274
Author(s):  
Lawrence H. Jaksha ◽  
David H. Evans
Keyword(s):  
New Mexico ◽  
Wave Velocity ◽  
Lower Crust ◽  
Seismic Waves ◽  
Seismic Refraction ◽  
Velocity Model ◽  
P Wave ◽  
Uppermost Mantle ◽  
P Wave Velocity ◽  
Crustal Thinning

Abstract A velocity model of the crust in northwestern New Mexico has been constructed from an interpretation of direct, refracted, and reflected seismic waves. The model suggests a sedimentary section about 3 km thick with an average P-wave velocity of 3.6 km/sec. The crystalline upper crust is 28 km thick and has a P-wave velocity of 6.1 km/sec. The lower crust below the Conrad discontinuity has an average P-wave velocity of about 7.0 km/sec and a thickness near 17 km. Some evidence suggests that velocity in both the upper and lower crust increases with depth. The P-wave velocity in the uppermost mantle is 7.95 ± 0.15 km/sec. The total crustal thickness near Farmington, New Mexico, is about 48 km (datum = 1.6 km above sea level), and there is evidence for crustal thinning to the southeast.

Sediment Thickness and Moho Depth Beneath Western Indonesian Region From Teleseismic Receiver Function

2021 ◽  
Author(s):  
Syaiful Bahri ◽  
Wiwit Suryanto ◽  
Drajat Ngadmanto
Keyword(s):  
Shear Wave ◽  
Shear Wave Velocity ◽  
Receiver Function ◽  
Velocity Model ◽  
Moho Depth ◽  
Sediment Layer ◽  
The North ◽  
East Kalimantan ◽  
Crust Layer ◽  
Teleseismic Receiver Function

Abstract The Earth's crust layer and sediment in Western Indonesia has been studied using the inversion of teleseismic receiver function from BMKG’s seismic network. Earthquake events were analyzed in this study with a moment magnitude greater than 6.0 with epicentral distances of 30° to 90°. A total of 60 earthquake events were observed and recorded by 91 stations around the study area. Furthermore, an inversion process was carried out using the initial velocity model from the modification of the AK135f velocity model to obtain the shear wave velocity structure below each stations. The velocity model from the azimuthally stacked vertical receiver function showed that the sediment layer had a relatively medium shear wave velocity value with an average of 2.1 km/s, while the crust layer had 4.60 km/s. The sedimentary layer thickness in this region also varies between 2 km to 10 km. A relatively thick sediment layer of about 8 km to 10 km was observed in two locations, in East Kalimantan associated with the Kutai Basin and Northern part of Sumatera in the North Sumatera Basin, a two major oil producer basinal area in Indonesia. The Moho discontinuity was also found at depths that vary between 16 km to 50 km. In addition, the most shallow Moho depth is 16 km below the North Kalimantan and North part of West Java, while the deeper Moho depth of 50 km is located below East Kalimantan, Central Kalimantan, North Sumatera and South Sumatera.

Thermodynamic constraints on assimilation of silicic crust by primitive magmas

2021 ◽  
Author(s):  
Jussi S Heinonen ◽  
Frank J Spera ◽  
Wendy A Bohrson
Keyword(s):  
Phase Equilibria ◽  
Lower Crust ◽  
Primitive Mantle ◽  
Upper Crust ◽  
Basaltic Composition ◽  
Primitive Magma ◽  
Partial Melts ◽  
Thermodynamic Limits ◽  
Melt Composition ◽  
Lower Crustal

&lt;p&gt;Some studies on basaltic and more primitive rocks suggest that their parental magmas have assimilated more than 50 wt.% (relative to the initial uncontaminated magma) of crustal silicate wallrock. But what are the thermodynamic limits for assimilation by primitive magmas? This question has been considered for over a century, first by N.L. Bowen and many others since then. Here we pursue this question quantitatively using a freely available thermodynamic tool for phase equilibria modeling of open magmatic systems &amp;#8212; the Magma Chamber Simulator (MCS; https://mcs.geol.ucsb.edu).&lt;/p&gt;&lt;p&gt;In the models, komatiitic, picritic, and basaltic magmas of various ages and from different tectonic settings assimilate progressive partial melts of average lower, middle, and upper crust. In order to pursue the maximum limits of assimilation constrained by phase equilibria and energetics, the mass of wallrock in the simulations was set at twice that of the initially pristine primitive magmas. In addition, the initial temperature of wallrock was set close to its solidus at a given pressure. Such conditions would approximate a rift setting with tabular chambers and high magma input causing concomitant crustal heating and steep geotherms.&lt;/p&gt;&lt;p&gt;Our results indicate that it is difficult for any primitive magma to assimilate more than 20&amp;#8722;30 wt.% of upper crust before evolving to intermediate/felsic compositions. However, if assimilant is lower crust, typical komatiitic magmas can assimilate more than their own weight (range of 59&amp;#8722;102 wt.%) and retain a basaltic composition. Even picritic magmas, more relevant to modern intraplate settings, have a thermodynamic potential to assimilate 28&amp;#8722;49 wt.% of lower crust before evolving into intermediate/felsic compositions.&lt;/p&gt;&lt;p&gt;These findings have important implications for petrogenesis of magmas. The parental melt composition and the assimilant heavily influence both how much assimilation is energetically possible in primitive magmas and the final magma composition. The fact that primitive mantle melts have potential to partially melt and assimilate significant fractions of (lower) crust may have fundamental importance for how trans-Moho magmatic systems evolve and how crustal growth is accomplished. Examples include generation of siliceous high-magnesium basalts in the Precambrian and anorogenic anorthosite-mangerite-charnockite-granite complexes with geochemical evidence of considerable geochemical overprint from (lower) crustal sources.&lt;/p&gt;

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