Numerical experiments in broadband receiver function analysis

1992 ◽  
Vol 82 (3) ◽  
pp. 1453-1474
Author(s):  
J. F. Cassidy

Abstract The use of broadband receiver function analysis to estimate the fine-scale S-velocity structure of the lithosphere is becoming increasingly popular. A series of numerical experiments shows several important aspects of this technique, with emphasis on estimation of dipping interfaces. The recent modification introduced to the receiver function analysis technique that preserves absolute amplitudes (Ammon, 1991) is more robust than the previous technique of modeling receiver functions that were normalized to unit amplitude. Using the latter method, shallow (e.g., depths less than ∼2 km) high-velocity contrast interfaces may alter the apparent amplitudes of Ps phases and produce inaccuracies in the Earth model developed. The use of absolute amplitudes minimizes this potential for error. When research targets include deep dipping structure, tight stacking bounds (e.g., ≦ 10° in backazimuth (BAZ) and epicentral distance (Δ)) should be applied to avoid attenuating Ps phases and to aid in the identification of reverberations or scattered energy. Reverberations sample a relatively large lateral range about the recording site (e.g., a radius of 1 to 1.5 times the depth of the reflecting interface) and in the presence of dipping interfaces exhibit drastic variations in amplitude and arrival time as a function of BAZ and Δ. Thus, they cannot readily be used to provide constraints on the Earth structure. Formal inversion techniques, which attempt to match all arrivals in the waveform, must be used with caution when modeling receiver functions from complex regions. Only those phases whose amplitude and arrival-time variations as a function of BAZ and Δ are consistent with those of Ps conversions should be modeled. Forward modeling may resolve, depending upon the data quality and noise level, S-velocity contrasts greater than ∼ 0.2 to 0.4 km / sec. Layers of thickness 2 to 5 km may be accurately imaged, and transition zones may be examined by considering various frequency bands of the data. In order to better understand the resolving power of the data, the averaging functions associated with the receiver functions may be calculated from the observed data and, if desired, used in the forward modeling process.

2021 ◽  
Author(s):  
Víctor Ortega ◽  
Luca D'Auria ◽  
Iván Cabrera-Pérez ◽  
José Barrancos ◽  
Germán D. Padilla ◽  
...  

<p>The receiver function analysis (RF) is a commonly used and well-established method to investigate crustal and mantle structures, removing the source, ray-path and instrument signatures. RF gives the unique signature of sharp seismic discontinuities and information about P and S wave velocities beneath a seismic station. In particular, using the direct P wave as a reference arrival time, and the relative arrival time of P-to-S (Ps) conversions and multiple reflections allow constraining the principal crustal structures and studying the effects of dipping interfaces and crustal layering.</p><p>We have applied RF analysis to the active volcanic islands of Tenerife and La Palma (Canary Islands). In recent years, both islands have increased their seismic activity and showed variation in geochemical parameters attributed to a magmatic-hydrothermal activity. Previous studies evidenced in La Palma and Tenerife a seismic Moho depth at 14 km and 12 and 15 km, respectively, but it is not clear because there are some others discontinuities under the stations (Lodge et al., 2012). Other RF studies indicated a depth of seismic Moho discontinuity between 16 and 30 km beneath the eastern islands to 11-15 km under the western isles, observing a thinning of the crust towards the west (Martinez-Arévalo et al., 2013). </p><p>We processed 313 teleseisms recorded by 17 stations for Tenerife and 252 teleseisms recorded by six stations for La Palma. Since the receiver functions display a significant complexity, as expected in oceanic volcanic islands, we applied a transdimensional inversion approach to image the 1D velocity structure beneath each station. We observe at least three discontinuities related with the oceanic crust and the overlying volcanic rocks layer. We compare the retrieved crustal structure with the seismicity recorded in recent years, showing how earthquakes have a radically different origin on these two islands. While in Tenerife they seem to be related to the dynamics of a shallow hydrothermal system, in La Palma they are related to magmatic intrusions in the upper mantle beneath the island.</p><p><strong>References</strong></p><p>Lodge, A., Nippress, S. E. J., Rietbrock, A., García-Yeguas, A., & Ibáñez, J. M. (2012). Evidence for magmatic underplating and partial melt beneath the Canary Islands derived using teleseismic receiver functions. Physics of the Earth and Planetary Interiors, 212, 44-54.</p><p>Martinez-Arevalo, C., de Lis Mancilla, F., Helffrich, G., & Garcia, A. (2013). Seismic evidence of a regional sublithospheric low velocity layer beneath the Canary Islands. Tectonophysics, 608, 586-599.</p>


2020 ◽  
Author(s):  
Víctor Ortega ◽  
Luca D'Auria

<p>The receiver function analysis (RF) is a commonly used and well-established method to investigate subsurface crustal and upper mantle structures, removing the source, ray-path and instrument signatures. RF gives the unique signature of sharp seismic discontinuities and information about P-wave (P) and shear-wave (Ps) velocity below the seismic station. In particular using the direct P-wave as a known reference arrival time, and the relative arrival time of P-to-S (Ps) conversions as well as PpPs, PsPs and PsSs reflections allow constraining the principal crustal structures and allows us to study the effects of dipping interfaces and crustal layering.</p><p>The aim of this work is to use the RF non-conventional analysis to study the crustal structures of Tenerife. Previous studies on receiver functions analysis an active oceanic volcanic island, showed that the Moho topography have a high dipping under the volcanic edifice and a depth ranging between 11 and 18 km depth. Furthermore, it has been observed that some phases related with a layer of volcanic rocks having a thickness of about 5.5 km and a P-wave velocity (Vp) of approximately 6 Km/s, lies above an old oceanic crust having a thickness of about 7 km and a Vp of about 6.8 km/s.</p><p>For this study we applied both time and frequency domain deconvolution to obtain receiver functions. The determination of the average crustal thickness and has been achieved by using the commonly uses H-k method. To constrain the internal crustal layering, we used a non-linear inversion algorithm based on full waveform modeling of the receiver function. Finally, we realized a modelling of the reflected and converted phases in the crust using seismic ray tracing. Our modelling takes into account the surface topography as well as an arbitrary geometry of the Moho.</p><p>In conclusion our results showed the presence of a thick layer (up to 5.5 km) of volcanic rocks in the central part of the island overlying an oceanic crust whose total thickness varied from 18 km in the central part to about 11 km in the peripheral areas. This work represents the first step toward further studies devoted at a finer imaging of the crustal structures of Tenerife using receiver function analysis.</p>


2020 ◽  
Vol 224 (2) ◽  
pp. 858-870
Author(s):  
Devajit Hazarika ◽  
Somak Hajra ◽  
Abhishek Kundu ◽  
Meena Bankhwal ◽  
Naresh Kumar ◽  
...  

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.


2020 ◽  
Author(s):  
Pınar Büyükakpınar ◽  
Mustafa Aktar

<p>This study focuses on the crust of the Eastern Marmara in order to understand of how much the structure is influenced by the tectonic history and also by the activity of the NAF. Recent studies have claimed that the crustal thickness varies significantly on the north and south of the NAF, which is assumed to indicate the separation line between Eurasian and Anatolian Plates. The present study aims to reevaluate the claim above, using newly available data and recently developed tools. The methods used during the study are the receiver function analysis and surface wave analysis. The first one is more intensively applied, since the second one only serves to introduce stability constraint in the inversions. Data are obtained from the permanent network of KOERI and from PIRES arrays.  The main result of the study indicates that the receiver functions for the stations close to the fault zone are essentially very different from the rest and should be treated separately. They show signs of complex 3D structures of which two were successfully analyzed by forward modeling (HRTX and ADVT). A dipping shallow layer is seen to satisfy the major part of the azimuthal variation at these two stations. For the stations off the fault on the other hand, the receiver functions show a more stable behavior and are analyzed successfully by classical methods. CCP stacking, H-k estimation, single and joint inversion with surface waves, are used for that purpose. The results obtained from these totally independent approaches are remarkably consistent with each other. It is observed that the crustal thickness does not vary significantly neither in the NS, nor in the SW direction. A deeper Moho can only be expected on two most NE stations where a gradual transition is more likely than a sharp boundary (SILT and KLYT). The structural trends, although not significant, are generally aligned in the EW direction.  In particular, a slower lower crust is observed in the southern stations, which is possibly linked to the mantle upwelling and thermal transient of the Aegean extension. Otherwise neither the velocity, nor the thickness of the crust does not imply any significant variation across the fault zone, as was previously claimed.</p>


2020 ◽  
Author(s):  
Zhipeng Zhou ◽  
Hans Thybo ◽  
Timothy Kusky ◽  
Chi-Chia Tang

<p>The crustal structure of the Anatolian plateau in Turkey is investigated using receiver functions obtained from the teleseismic recordings of the Kandilli Observatory array (KOERI; KO) and the available IRIS data (e.g., Eastern Turkey Seismic Experiment (ETSE), Northern Anatolian Fault experiment (YL), Continental Dynamics–Central Anatolian Tectonics (CD-CAT) project). The following steps are included for studying the crustal structures in Anatolia Plate: 1) high-resolution crustal structures inferred from Receiver Function (RF) inversion algorithm using multiple-taper correlation (MTC) estimates, we try to distinguish interfaces including Moho, bottom of partial melting and other interfaces by the Ps phase; 2) we calculate RFs by Time Domain Interactive Deconvolution and transform the time domain RFs into the H-Vp/Vs (H-k) domain to find the best fit Moho and Vp/Vs, we classify the quality of the H-k stacking results and record all the possible H-k couples; 3) we determine the H-k values for the stations with low quality by comparing the RF H-k stacking results with nearby stations with good quality. With the dense stations, we present high-quality Moho variations and crustal structures in the Anatolia Plate.</p>


2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Aki Ito ◽  
Takashi Tonegawa ◽  
Naoki Uchida ◽  
Yojiro Yamamoto ◽  
Daisuke Suetsugu ◽  
...  

Abstract We applied tomographic inversion and receiver function analysis to seismic data from ocean-bottom seismometers and land-based stations to understand the structure and its relationship with slow slip events off Boso, Japan. First, we delineated the upper boundary of the Philippine Sea Plate based on both the velocity structure and the locations of the low-angle thrust-faulting earthquakes. The upper boundary of the Philippine Sea Plate is distorted upward by a few kilometers between 140.5 and 141.0°E. We also determined the eastern edge of the Philippine Sea Plate based on the delineated upper boundary and the results of the receiver function analysis. The eastern edge has a northwest–southeast trend between the triple junction and 141.6°E, which changes to a north–south trend north of 34.7°N. The change in the subduction direction at 1–3 Ma might have resulted in the inflection of the eastern edge of the subducted Philippine Sea Plate. Second, we compared the subduction zone structure and hypocenter locations and the area of the Boso slow slip events. Most of the low-angle thrust-faulting earthquakes identified in this study occurred outside the areas of recurrent Boso slow slip events, which indicates that the slow slip area and regular low-angle thrust earthquakes are spatially separated in the offshore area. In addition, the slow slip areas are located only at the contact zone between the crustal parts of the North American Plate and the subducting Philippine Sea Plate. The localization of the slow slip events in the crust–crust contact zone off Boso is examined for the first time in this study. Finally, we detected a relatively low-velocity region in the mantle of the Philippine Sea Plate. The low-velocity mantle can be interpreted as serpentinized peridotite, which is also found in the Philippine Sea Plate prior to subduction. The serpentinized peridotite zone remains after the subduction of the Philippine Sea Plate and is likely distributed over a wide area along the subducted slab.


2018 ◽  
Author(s):  
Chengping Chai ◽  
Monica Maceira ◽  
Charles Ammon ◽  
Carene Larmat ◽  
Sridhar Anandakrishnan ◽  
...  

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