scholarly journals Structural Characteristics of Moho Surface Based on Time Series Function of Natural Earthquakes

2021 ◽  
Vol 13 (4) ◽  
pp. 763
Author(s):  
Xuelei Li ◽  
Zhuo Jia ◽  
Nanqiao Du ◽  
Yi Xu ◽  
Gongbo Zhang
Keyword(s):  
Seismic Wave ◽  
Velocity Structure ◽  
Deep Structure ◽  
Receiver Function ◽  
Structural Characteristics ◽  
Velocity Ratio ◽  
Tectonic Activity ◽  
Volcanic Area ◽  
Long Distance ◽  
Reflection Characteristics

Remote sensing is a non-contact, long-distance detection technology. The reflection characteristics of a seismic wave can be used to detect remote and non-contact targets. Based on the reflection characteristics of a seismic wave, the underground structure in Tengchong Volcanic Area is explored. In order to further study the deep structure and magmatic activity of the crust in the volcanic area, we carried out a one-year mobile seismic observation. In this paper, nine broadband seismic stations were set up in the Tengchong Volcanic Area, and 3350 receiver function waveforms were collected. The crustal thickness, average wave velocity ratio, and Poisson’s ratio below these stations were calculated by the receiver function method, and the velocity structure near the Moho below these stations was evaluated. Combined with topographic data from SRTM3 (Shuttle Radar Topography Mission 3), this study reveals the dynamic relationship among crustal structure, crustal magmatism, and regional tectonic movement. Mantle upwelling plays an important role on the Moho uplift in the northern Tengchong Volcanic Area, and there are interconnected intracrustal magma chambers in the upper platform. The evaluation results of the Moho transition zone also indicate that the Dayingjiang fault is closely related to the tectonic activity of the Tengchong Volcanic fault.

Joint receiver function and gravity inversion for new constraints on the Ivrea body structure: a 2D high-resolution view along the Val Sesia profile (N. Italy).

2021 ◽  
Author(s):  
Matteo Scarponi ◽  
György Hetényi ◽  
Jaroslava Plomerová ◽  
Stefano Solarino
Keyword(s):  
High Resolution ◽  
Velocity Structure ◽  
Receiver Function ◽  
Joint Inversion ◽  
Gravity Data ◽  
Rock Physics ◽  
Receiver Functions ◽  
Gravity Inversion ◽  
European Alps ◽  
Horizontal Distance

<p>We present results from a joint inversion study of new seismic and gravity data to constrain a 2D high-resolution image of one of the most prominent geophysical anomalies of the European Alps: the Ivrea geophysical body (IGB). Our work exploits both new data and multidisciplinary a priori constraints, to better resolve the shallow crustal structure in the Ivrea-Verbano zone (IVZ), where the IGB is known to reach anomalously shallow depths and partially outcrop at the surface.</p><p>A variety of previous studies, ranging from gravity surveys to vintage refraction seismics and recent local earthquake tomographies (Solarino et al. 2018, Diehl et al. 2009), provide comprehensive but spatially sparse information on the IGB structure, which we aim at investigating at higher resolution, along a linear profile crossing the IVZ. To this purpose, we deployed 10 broadband seismic stations (MOBNET pool, IG CAS Prague), 5 km spaced along a linear West-East profile, along Val Sesia and crossing Lago Maggiore. This network operated for 27 months and allowed us to produce a new database of ca. 1000 seismic high-quality receiver functions (RFs). In addition, we collected new gravity data in the IVZ, with a data coverage of 1 gravity point every 1-2 km along the seismic profile. The newly collected data was used to set up an inversion scheme, in which RFs and gravity anomalies are jointly used to constrain the shape and the physical property contrasts across the IGB interface.</p><p>We model the IGB as a single interface between far-field constraints, whose geometry is defined by the coordinates of four nodes which may vary in space, and  density and V<sub>S</sub> shear-wave velocity contrasts associated with the interface itself, varying independently. A Markov chain Monte Carlo (MCMC) sampling method with Metropolis-Hastings selection rule was implemented to efficiently explore the model space, directing the search towards better fitting areas.</p><p>For each model, we perform ray-tracing and RFs migration using the actual velocity structure both for migration and computation of synthetic RFs, to be compared with the observations via cross-correlation of the migration images. Similarly, forward gravity modelling for a 2D density distribution is implemented and the synthetic gravity anomaly is compared with the observations along the profile. The joint inversion performance is the product of these two misfits.</p><p>The inversion results show that the IGB reaches the shallowest depths in the western part of the profile, preferentially locating the IGB interface between 3 and 7 km depth over a horizontal distance of ca. 20 km (between Boccioleto and Civiasco, longitudes 8.1 and 8.3). Within this segment, the shallowest point reaches up to 1 km below sea level. The found density and velocity contrasts are in agreement with rock physics properties of various units observed in the field and characterized in earlier studies.</p>

Crustal structure in the southern Bering Shelf and the Alaska Peninsula from inversion of surface-wave dispersion data

1989 ◽  
Vol 79 (6) ◽  
pp. 1883-1893
Author(s):  
Mansour Niazi ◽  
Kin-Yip Chun
Keyword(s):  
Crustal Structure ◽  
Velocity Structure ◽  
Structural Characteristics ◽  
Resolving Power ◽  
Surface Wave Dispersion ◽  
Bristol Bay ◽  
Alaska Peninsula ◽  
South Central ◽  
Bering Shelf ◽  
Group Velocities

Abstract Dispersion of surface waves in the southern Bering Shelf (Bristol Bay) and the Alaska Peninsula is investigated for a study of the regional crustal structure. Our data consist of five shallow earthquakes located along the Aleutian Arc and recorded by long-period, three-component seismographs sited in south-central Alaska. Both Love and Rayleigh group velocities are obtained through the application of the phase-matched filtering technique. The results are converted to equivalent pure-path data by appropriate adjustment using the published information for the continental Alaska. Treating the shear velocity of each layer as an independent parameter, the pure-path group velocities of Love and Rayleigh waves are jointly inverted in order to obtain a satisfactory agreement between the theoretical and the observed dispersion characteristics. Estimates of the resolving power of the inversion and uncertainty of the final velocity structure show substantial improvement over the previously published models. With their crustal thicknesses ranging between 33 and 36 km, none of the final models displays structural characteristics reminiscent of an oceanic crust. Over the northernmost path across the Bristol Bay, we found an indication of a weak low-velocity zone (five per cent reduction relative to the lid velocity) whose prominence diminishes towards the south.

scholarly journals Assessing uncertainties in high-resolution, multifrequency receiver-function inversion: A comparison with borehole data

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. KS11-KS22 ◽  
Author(s):  
Nicola Piana Agostinetti ◽  
Alberto Malinverno
Keyword(s):  
Wave Velocity ◽  
Receiver Function ◽  
Joint Inversion ◽  
Seismic Station ◽  
Velocity Ratio ◽  
Earth Model ◽  
Elastic Model ◽  
S Wave ◽  
Borehole Data ◽  
Sonic Log

We use teleseismic P-to-S converted waves from a permanent station to estimate the uncertainties in a 1D elastic model of the shallow crust (0–7 km depth) obtained from the inversion of receiver function (RF) data. Our earth model consists of layers with a constant S-wave velocity [Formula: see text] and P- to S-wave velocity ratio ([Formula: see text]). We apply a Bayesian formulation and transdimensional Monte Carlo sampling to compute the posterior uncertainties of the earth model. The model uncertainties rely on a realistic representation of the data uncertainties, and we estimate directly from the stacking of the teleseismic data, a full-error covariance matrix. To explore the effect of the number of teleseismic events and the RF frequency content, we compare the results of inverting a single RF computed for a cut-off filter frequency of 4 Hz with the joint inversion of four RFs computed from independent ensembles in a larger pool of events for cut-off frequencies of 0.5, 1, 2, and 4 Hz. The inversion results are compared with the lithostratigraphy and sonic-log measurements from a 7 km deep borehole drilled near the seismic station. The inversion of a single RF results in larger uncertainties in the recovered [Formula: see text] profile and in the depth to seismic discontinuities compared with the multifrequency inversion. Moreover, the multifrequency inversion predicts more accurately the depth to a velocity inversion at approximately 6 km below the surface and matches more closely the borehole sonic-log data. Our results indicate that RF data can be used to map shallow (3–5 km depth) crustal interfaces with uncertainties in the order of 300–500 m, whereas uncertainties are consistently smaller (<300 m) for interfaces in the top kilometer.

Using the receiver function for studying earth deep structure in the Southern Borborema Province

2019 ◽  
Vol 94 ◽  
pp. 102221
Author(s):  
Chris B. Fianco ◽  
George Sand França ◽  
Diogo Farrapo Albuquerque ◽  
Carlos da Silva Vilar ◽  
Roberto Max Argollo
Keyword(s):  
Deep Structure ◽  
Receiver Function ◽  
Borborema Province

HIGH RESOLUTION VELOCITY STRUCTURE OF THE NORTH CHINA CRATON BASEMENT BY BLASTING SEISMIC WAVE-RESULTS FROM DAFENG-BAOTOU REFRACTION PROFILE

2017 ◽  
Vol 60 (5) ◽  
pp. 505-519
Author(s):  
ZHAO Jin-Ren ◽  
LIU Bao-Jin ◽  
DUAN Yong-Hong ◽  
PAN Su-Zhen ◽  
FAN Zhen-Yu ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Wave ◽  
North China Craton ◽  
North China ◽  
Velocity Structure ◽  
The North

A new inversion method to construct a 3-D crustal shear-wave velocity model from P-to-S converted waves and application to the Central Alps

2020 ◽  
Author(s):  
Leonardo Colavitti ◽  
György Hetényi ◽  
AlpArray Working Group
Keyword(s):  
Simulated Annealing ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Receiver Function ◽  
Velocity Model ◽  
Central Alps ◽  
Travelling Salesman ◽  
The Given

&lt;p&gt;We developed a new method where teleseismic P-to-S converted waves are used to construct a fully 3-D shear-wave velocity model of the crust. The method differs from ambient noise and local earthquake tomography in its ray-paths being closer to vertical. Our approach requires a dense seismological network, and we first focus on the Central Alps considering the available permanent and temporary station datasets (e.g., Het&amp;#233;nyi et al., 2018, Surv. Geophys.).&lt;/p&gt;&lt;p&gt;We implemented an accurate ray-propagator which respects Snell&amp;#8217;s law in 3-D at any interface geometry. Following a teleseismic P ray propagator (Knapmeyer, 2004) from event to station which uses a 1-D global velocity model (iasp91), P-to-S conversion at the Moho is calculated for the crustal S ray considering the true local dip. The corresponding arrival to the surface is typically several km away from the station, which we then adjust by changing the ray-parameter.&amp;#160;In the Central Alps, using the 3-D P-velocity structure of Diehl et al. (2009) and the local Moho geometry of Spada et al. (2013), the mean distance between the arriving S-wave and the station is about 150 m (median ca. 40 m).&lt;/p&gt;&lt;p&gt;For our approach we adopt a new model parameterization of velocities. It is rectangular in map view (nodes at 25x25 km in the Alps), while in depth we define a 2-layer model with separate velocities above and below each discontinuity. The introduction of this flexibility allows us to accommodate a velocity gradient within each layer and investigate velocity jumps across discontinuities.&lt;/p&gt;&lt;p&gt;The inversion proceeds iteratively, by visiting every node of the map following a Travelling Salesman Path. At each node, receiver function rays in the surrounding volume are considered for inversion, and bundled into sub-blocks and ranges of back-azimuth (5x5 km size, 45&amp;#176; or 60&amp;#176; bins for the Central Alps). The velocity model at the given node is inverted using the technique of Simulated Annealing, followed by a pattern search algorithm to avoid falling in a local minimum. During iterations of the Simulated Annealing, individual velocity model corresponding to each receiver function is extracted from the 3-D model along its ray path.&lt;/p&gt;&lt;p&gt;The inversion proceeds for 4 or 5 independent parameters: Moho and a hypothetical intra-crustal discontinuity depth, Vp/Vs ratio (either full crust, or separately for upper and lower crust) and the P-wave velocity jump at the intra-crustal discontinuity. Finally, the velocity structure is updated with the result obtained at the given node. We observe that a few rounds of Travelling Salesman Paths improve the overall misfit.&lt;/p&gt;&lt;p&gt;First results on the Central Alps show that the Moho depth generally reflects well the roots of the Alpine orogen. Resolving crustal Vp/Vs ratio is more stable when considering the full crust, instead of two separate layers. The Conrad discontinuity remains difficult to resolve. The obtained velocity structure is compared along profiles to recent Vs results from 3-D ambient noise tomography (Lu et al., 2018).&lt;/p&gt;

2D velocity profiles along south- and northwestern Norway: An approach using receiver function analysis and Markov chains

2020 ◽  
Author(s):  
Marco Brönner ◽  
Claudia Pavez
Keyword(s):  
Deep Structure ◽  
Receiver Function ◽  
Function Analysis ◽  
Velocity Model ◽  
Reversible Jump ◽  
Moho Discontinuity ◽  
Mantle Transition Zone ◽  
Temporary Network ◽  
Receiver Function Analysis ◽  
Teleseismic Events

&lt;p&gt;A receiver function analysis was carried out along two profiles located in north- and southwestern Norway. We selected and processed 801 teleseismic events registered by twelve seismic stations belonging to the 2002-2005 Geofon/Aarhus temporary network. The HK (depth vs Vp/Vs) stacking procedure and a Reversible jump Markov chain Monte Carlo (Rj-McMC) inversion were applied independently with the objective to reveal new crustal and crust-mantle transitional contrasts gaining a better understanding of the geology. In the southern profile, the most noticeable feature corresponds to a Moho offset of about ~5 km ca. 85 km to the east of the Norwegian coast: That feature was previously observed in several occasions and is also well-supported from this research. Furthermore, a very deep Moho discontinuity &amp;#8211; at between 45 &amp;#8211; 50 km depth - was found beneath the northern profile, approximately 70 km inland from the coast, and dipping about 30&amp;#176; to the northwest. Even when this deep structure was previously inferred through other methods, its presence was not certainly confirmed and so far, the origin of this feature is still disputed. We discuss two hypotheses, which are valid to explain the occurrence of the noticeable anomaly. First, a gradual and wide crust-mantle transition zone, which is also reflected in the velocity model or second, the presence of a paleo-slab of Fennoscandian basement subducted and deformed during the Caledonian Orogen (490-390 Ma).&lt;/p&gt;

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