Common-Reflection-Point-Based Prestack Depth Migration for Imaging Lithosphere in Python: Application to the Dense Warramunga Array in Northern Australia

2020 ◽  
Vol 91 (5) ◽  
pp. 2890-2899 ◽  
Author(s):  
Weijia Sun ◽  
Brian L. N. Kennett
Keyword(s):  
Open Source ◽  
Receiver Function ◽  
Function Analysis ◽  
Vertical Component ◽  
P Wave ◽  
Northern Australia ◽  
Reflection Point ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Conversion Point

Abstract We exploit estimates of P-wave reflectivity from autocorrelation of transmitted teleseismic P arrivals and their coda in a common reflection point (CRP) migration technique. The approach employs the same portion of the vertical-component seismogram, as in standard Ps receiver function analysis. This CRP prestack depth migration approach has the potential to image lithospheric structures on scales as fine as 4 km or less. The P-wave autocorrelation process and migration are implemented in open-source software—the autocorrelogram calculation (ACC) package, which builds on the widely used the seismological Obspy toolbox. The ACC package is written in the open-source and free Python programming language (3.0 or newer) and has been extensively tested in an Anaconda Python environment. The package is simple and friendly to use and runs on all major operating systems (e.g., Windows, macOS, and Linux). We utilize Python multiprocessing parallelism to speed up the ACC on a personal computer system, or servers, with multiple cores and threads. The application of the ACC package is illustrated with application to the closely spaced Warramunga array in northern Australia. The results show how fine-scale structures in the lithospheric can be effectively imaged at relatively high frequencies. The Moho ties well with conventional H−κ receiver analysis and deeper structure inferred from stacked autocorrelograms for continuous data. CRP prestack depth migration provides an important complement to common conversion point receiver function stacks, since it is less affected by surface multiples at lithospheric depths.

scholarly journals Preliminary Results of Receiver Function Forward Velocity Modelling at Merapi Volcano

2021 ◽  
Vol 873 (1) ◽  
pp. 012056
Author(s):  
M F R Auly ◽  
A K Ilahi ◽  
I Madrinovella ◽  
S Widyanti ◽  
S K Suhardja ◽  
...  
Keyword(s):  
Receiver Function ◽  
Tectonic Setting ◽  
Vertical Component ◽  
P Wave ◽  
Function Technique ◽  
Boundary Current ◽  
Low Velocity ◽  
Mantle Boundary ◽  
Velocity Models ◽  
Synthetic Model

Abstract The tectonic setting of Java island, located at southwestern edge of the Eurasia continent, is dominated by the subduction of Indo-Australia plate. One of the characteristics of active subduction is active seismicity, the generation of arc magmatism and volcanic activity. Mt. Merapi is one example of active volcano related with the subduction process. It is one of the most active volcanoes with location close to high population area. To better understand this area, we employed the Receiver Function technique, a method to image sub surface structure by removing the vertical component from horizontal component. First, we collected high magnitude events and processed RF with water level deconvolution method. Then, we constructed synthetic model with initial velocity input from previous tomography model. Note that we used reflectivity method in generating synthetic model with input parameters matched with parameters from real data processing. Next, we adjusted velocity inputs mainly on tops sediments (1-3 km) to include sediment layers and volcanic rocks, mid-depth low velocity zone that may be related with magma chamber and depth of crust-mantle boundary. Current forward velocity models show a relatively good agreement from 3 stations (ME25, ME32 and ME36). We estimate a thin layer of sediments followed a zone of velocity layer at a depth of 10-15 km and crust-mantle boundary ranging from 26-29 km. In this study, simulated that the signal of sediments layer and low velocity layers interfere main crust mantle boundary that supposed to be highest signal after the P wave in the typical receiver function study.

The CIELO Seismic Experiment

2021 ◽  
Author(s):  
Heather A. Ford ◽  
Maximiliano J. Bezada ◽  
Joseph S. Byrnes ◽  
Andrew Birkey ◽  
Zhao Zhu
Keyword(s):  
Receiver Function ◽  
Function Analysis ◽  
P Wave ◽  
Crust And Upper Mantle ◽  
Waveform Data ◽  
Wyoming Craton ◽  
Sensor Orientation ◽  
Seismic Experiment ◽  
Short Period ◽  
Receiver Function Analysis

Abstract The Crust and lithosphere Investigation of the Easternmost expression of the Laramide Orogeny was a two-year deployment of 24 broadband, compact posthole seismometers in a linear array across the eastern half of the Wyoming craton. The experiment was designed to image the crust and upper mantle of the region to better understand the evolution of the cratonic lithosphere. In this article, we describe the motivation and objectives of the experiment; summarize the station design and installation; provide a detailed accounting of data completeness and quality, including issues related to sensor orientation and ambient noise; and show examples of collected waveform data from a local earthquake, a local mine blast, and a teleseismic event. We observe a range of seasonal variations in the long-period noise on the horizontal components (15–20 dB) at some stations that likely reflect the range of soil types across the experiment. In addition, coal mining in the Powder River basin creates high levels of short-period noise at some stations. Preliminary results from Ps receiver function analysis, shear-wave splitting analysis, and averaged P-wave delay times are also included in this report, as is a brief description of education and outreach activities completed during the experiment.

Imaging the Moho and Main Himalayan Thrust beneath the Kumaon Himalaya: constraints from receiver function analysis

2020 ◽  
Vol 224 (2) ◽  
pp. 858-870
Author(s):  
Devajit Hazarika ◽  
Somak Hajra ◽  
Abhishek Kundu ◽  
Meena Bankhwal ◽  
Naresh Kumar ◽  
...  
Keyword(s):  
Poisson’S Ratio ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Thickness ◽  
Receiver Functions ◽  
P Wave ◽  
Poisson's Ratio ◽  
Kumaon Himalaya ◽  
Receiver Function Analysis ◽  
Lower Crustal

SUMMARY We analyse P-wave receiver functions across the Kumaon Himalaya and adjoining area to constrain crustal thickness, intracrustal structures and seismic velocity characteristics to address the role of the underlying structure on seismogenesis and geodynamic evolution of the region. The three-component waveforms of teleseismic earthquakes recorded by a seismological network consisting of 18 broad-band seismological stations have been used for receiver function analysis. The common conversion point (CCP) depth migrated receiver function image and shear wave velocity models obtained through inversion show a variation of crustal thickness from ∼38 km in the Indo-Gangetic Plain to ∼42 km near the Vaikrita Thrust. A ramp (∼20°) structure on the Main Himalayan Thrust (MHT) is revealed beneath the Chiplakot Crystalline Belt (CCB) that facilitates the exhumation of the CCB. The geometry of the MHT observed from the receiver function image is consistent with the geometry revealed by a geological balanced cross-section. A cluster of seismicity at shallow to mid-crustal depths is detected near the MHT ramp. The spatial and depth distribution of seismicity pattern beneath the CCB and presence of steep dipping imbricate faults inferred from focal mechanism solutions suggest a Lesser Himalayan Duplex structure in the CCB above the MHT ramp. The study reveals a low-velocity zone (LVZ) with a high Poisson's ratio (σ ∼0.28–0.30) at lower crustal depth beneath the CCB. The high value of Poisson's ratio in the lower crust suggests the presence of fluid/partial melt. The shear heating in the ductile regime and/or decompression and cooling associated with the exhumation of the CCB plausibly created favorable conditions for partial melting in the lower crustal LVZ.

Anisotropic parsimonious prestack depth migration

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. S25-S36 ◽  
Author(s):  
Ernesto V. Oropeza ◽  
George A. McMechan
Keyword(s):  
Model Building ◽  
Computing Time ◽  
Synthetic Data ◽  
Transversely Isotropic ◽  
Velocity Model ◽  
P Wave ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Tti Media ◽  
Map Migration

An efficient Kirchhoff-style prestack depth migration, called “parsimonious” migration, was developed a decade ago for isotropic 2D and 3D media by using measured slownesses to reduce the amount of ray tracing by orders of magnitude. It is conceptually similar to “map” migration, but its implementation has some differences. We have extended this approach to 2D tilted transversely isotropic (TTI) media and illustrated it with synthetic P-wave data. Although the framework of isotropic parsimonious may be retained, the extension to TTI media requires redevelopment of each of the numerical components, calculation of the phase and group velocity for TTI media, development of a new two-point anisotropic ray tracer, and substitution of an initial-angle isotropic shooting ray-trace algorithm for an anisotropic one. The model parameterization consists of Thomsen’s parameters ([Formula: see text], [Formula: see text], [Formula: see text]) and the tilt angle of the symmetry axis of the TI medium. The parsimonious anisotropic migration algorithm is successfully applied to synthetic data from a TTI version of the Marmousi2 model. The quality of the image improves by weighting the impulse response by the calculation of the anisotropic Fresnel radius. The accuracy and speed of this migration makes it useful for anisotropic velocity model building. The elapsed computing time for 101 shots for the Marmousi2 TTI model is 35 s per shot (each with 501 traces) in 32 Opteron cores.

scholarly journals Crustal Structure Study in Lampung Region Using Teleseismic Receiver Function Analysis

2021 ◽  
Vol 2110 (1) ◽  
pp. 012002
Author(s):  
A R Puhi ◽  
P Ariyanto ◽  
B Pranata ◽  
B S Prayitno
Keyword(s):  
Wave Velocity ◽  
Crustal Structure ◽  
Receiver Function ◽  
Function Analysis ◽  
P Wave ◽  
Sediment Layer ◽  
Eurasian Plate ◽  
S Wave ◽  
Near Surface ◽  
Sumatran Fault

Abstract Lampung region is seismically and volcanic active because located in subduction zone of Indo-Australian and Eurasian plate. We applied receiver function and stacking H-k analysis to estimate the crustal structure in Lampung region. We used teleseismic earthquake data (epicenter distance 30°-90°) and M>6 recorded at 3 seismic broadband stations owned by Agency for Meteorology Climatology and Geophysics (BMKG). Those stations are PSLI (located on Sebesi Island approximately 20 km from Anak Krakatau) represented volcanic arc zone, KASI (located on Kota Agung, Lampung) represented Sumatran Fault Zone and KLI (located on Kotabumi, Lampung) represented back-arc basin. Crustal thickness estimated at PSLI station 32-36 km, KASI station 36-40 km, and KLI station 30-36 km. Furthermore, in 3 stations P wave velocity estimated 4.1-11 km/s, S wave velocity 2.2-6.2 km/s, while vp/vs value estimated 1.7-2.05. We estimated Anak Krakatau volcano’s magma chamber beneath PSLI station in depth 16-30 km, Great Sumatran Fault structure in depth about 8-14 km beneath KASI station, and thick sediment layer about 4 km near surface beneath KLI station. This study result is expected to explain more detail crustal of Lampung region and can be useful for developing of BMKG’s seismic monitoring systems and other geophysical fields in future.

Traveltime calculation and prestack depth migration in tilted transversely isotropic media

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Dhananjay Kumar ◽  
Mrinal K. Sen ◽  
Robert J. Ferguson
Keyword(s):  
Direct Method ◽  
Transversely Isotropic ◽  
Vertical Axis ◽  
P Wave ◽  
Fourier Series Expansion ◽  
Prestack Depth Migration ◽  
Thrust Sheet ◽  
Depth Migration ◽  
Axis Of Symmetry ◽  
Tti Media

The principal objective of our work is to develop a technique for prestack depth migration in tilted transversely isotropic (TTI) media in which the axis of symmetry is not vertical and may be spatially varying. Such models are required to image seismic data in geologically complex regions such as the Canadian Foothills. We have developed a 2D Kirchhoff integral‐based migration algorithm in which the traveltime computation comprises the major task. Among the existing traveltime computation algorithms such as ray tracing with interpolation, ray bending, and eikonal solvers, a direct or a brute force approach of traveltime computation is generally highly robust. We have modified a direct method of first‐arrival P‐wave traveltime computation in 2D media that accounts for TTI. The algorithm requires that the group velocity be computed at each gridpoint, using either an analytic solution or by an approximate Fourier series expansion. The P‐wave traveltime contours computed for complex geologic models show the pronounced effects from TTI media. Our results, using laboratory P‐wave data collected over a physical model of an anisotropic thrust sheet, reveal that a 2D Kirchhoff migration based on our traveltime algorithm (TTI model) images the structure beneath the thrust sheet very well. The vertical transversely isotropic (assuming a vertical axis of symmetry) or isotropic imaging introduces false anticlinal structures. We compare our results with those obtained by a recursive‐extrapolation method and find that our approach images the underside of one of the thrust sheets better.

Unexpected Consequences of Transverse Isotropy

2020 ◽  
Author(s):  
Hitoshi Kawakatsu
Keyword(s):  
Rayleigh Wave ◽  
Wave Velocity ◽  
Seismic Analysis ◽  
Receiver Function ◽  
Function Analysis ◽  
Incidence Angle ◽  
Body Wave ◽  
Transverse Isotropy ◽  
P Wave ◽  
S Wave

ABSTRACT In a series of articles, Kawakatsu et al. (2015) and Kawakatsu (2016a,b, 2018) introduced and discussed a new parameter, ηκ, that characterizes the incidence angle dependence (relative to the symmetry axis) of seismic body-wave velocities in a transverse isotropy (TI) system. During the course of these exercises, several nontrivial consequences of TI were realized and summarized as follows: (1) P-wave velocity (anisotropy) strongly influences the conversion efficiency of P-to-S and S-to-P, as much as S-wave velocity perturbation does; (2) Rayleigh-wave phase velocity has substantial sensitivity to P-wave anisotropy near the surface; (3) a trade-off exists between ηκ and the VP/VS ratio if the latter is sought under an assumption of isotropy or the elliptic condition. Among these findings, the first two deserve careful attention in interpretation of results of popular seismic analysis methods, such as receiver function analysis and ambient-noise Rayleigh-wave dispersion analysis. We present simple example cases for such problems to delineate the effect in actual situations, as well as scalings among TI parameters of the crust and mantle materials or models that might help understanding to what extent the effect becomes important.

Seismic P-wave receiver function modelling of Archean cratonic crust: A global perspective

2020 ◽  
Author(s):  
Poulami Roy ◽  
Kajaljyoti Borah
Keyword(s):  
Continental Crust ◽  
Receiver Function ◽  
Function Analysis ◽  
Crustal Thickness ◽  
Global Perspective ◽  
P Wave ◽  
Evolution Process ◽  
S Wave ◽  
Economic Significance ◽  
Formation And Evolution

<p>Cratons are representative of the oldest cores of continental crusts. Study of cratons is important  as they preserve the pristine nature of continental crusts as well as they have economic significance as a major source of the world's mineral deposits. The crustal thickness, crustal composition, structure and physical properties of crust-mantle transition (the Moho) are the key parameters for understanding the formation and evolution of continental crust. The ratio of  seismic P-wave and S-wave velocity (Vp/Vs) is used as a parameter to understand the petrologic nature of the Earth's crust. Using these parameters, we address the crustal properties of all Archean cratons. The teleseismic P-wave receiver function analysis reveals that all the Eoarchean (4-3.6 Ga) cratons (Superior, North Atlantic Craton, North China Craton, Yilgarn, Zimbabwe, Kaapvaal) have crustal thickness ranges between 34-42 km and Vp/Vs ratio 1.68-1.79, the Paleoarchean (3.6-3.2 Ga) cratons (Baltic shield, Pilbara, Tanzania, Grunehogna) have 29-52 km crustal thickness and Vp/Vs ratio 1.7-1.85, the Mesoarchean (3.2-2.8 Ga) cratons (Sao Francisco, Guapore, Yangtze, Antananarivo) have 36-53 km thickness and Vp/Vs ratio 1.7-1.9, and Neoarchean (2.8-2.5 Ga) cratons (Guiana, Anabar, Gawler, Napier, Tarim) have 36-59 km thickness and Vp/Vs ratio 1.64-1.95. The nature of crust-mantle transition is overall sharp and flat.  We also found that the crusts which are stabilized earlier, are thinner compared to the later stabilized crusts. Our findings are well-correlated with the craton evolution process predicted by Durrheim and Mooney (1994), where older crusts are thin due to delamination process and relatively younger crusts are thick due to basaltic underplating. Our result of higher Vp/Vs ratio in the relatively younger crusts corroborates with the mafic nature of the crust whereas the older crusts are felsic-intermediate resulting lower Vp/Vs ratio. Our study is unique as it includes most of the global cratons and suggests a global model of continental crust formation and evolution process.</p>

Identifying, removing, and imaging P‐S conversions at salt‐sediment interfaces

Geophysics ◽  
2003 ◽  
Vol 68 (3) ◽  
pp. 1052-1059 ◽  
Author(s):  
Richard S. Lu ◽  
Dennis E. Willen ◽  
Ian A. Watson
Keyword(s):  
P Wave ◽  
Time Interval ◽  
S Wave ◽  
Converted Wave ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Time Migration ◽  
Wave Imaging ◽  
Wave Image ◽  
Converted Waves

The large velocity contrast between salt and the surrounding sediments generates strong conversions between P‐ and S‐wave energy. The resulting converted events can be noise on P‐wave migrated images and should be identified and removed to facilitate interpretation. On the other hand, they can also be used to image a salt body and its adjacent sediments when the P‐wave image is inadequate. The converted waves with smaller reflection and transmission angles and much larger critical angles generate substantially different illumination than does the P‐wave. In areas where time migration is valid, the ratio between salt thickness in time and the time interval between the P‐wave and the converted‐wave salt base on a time‐migrated image is about 2.6 or 1.3, depending upon whether the seismic wave propagates along one or both of the downgoing and upcoming raypaths in salt as the S‐wave, respectively. These ratios can be used together with forward seismic modeling and 2D prestack depth migration to identify the converted‐wave base‐of‐salt (BOS) events in time and depth and to correctly interpret the subsalt sediments. It is possible to mute converted‐wave events from prestack traces according to their computed arrival times. Prestack depth migration of the muted data extends the updip continuation of subsalt sedimentary beds, and improves the salt–sediment terminations in the P‐wave image. Prestack and poststack depth‐migrated examples illustrate that the P‐wave and the three modes of converted waves preferentially image different parts of the base of salt. In some areas, the P‐wave BOS can be very weak, obscured by noise, or completely absent. Converted‐wave imaging complements P‐wave imaging in delineating the BOS for velocity model building.

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