Earthquake data collected by the INDEPTH-II Passive-Source Experiment show that there is a substantial south to north variation in velocity structure of crust beneath southern Tibet. North Zangbo suture, Lhasa block, midcrustal low-velocity zone revealed inversion receiver functions, Rayleigh-wave phase velocities, and modeling radial component teleseismic P-waveforms. Conversely, Tethyan Himalaya, no was observed. The presence implies partially molten layer middle northern Yadong-Gulu rift...

Pn travel times are affected not only by lateral variations in crust and mantle velocity but also significant amounts of laterally varying anisotropy. To investigate uppermost anisotropy, a tomography algorithm was reformulated to include both horizontal it applied time data from the western United States. Results show that anisotropy is as important explaining residuals variations. A detailed resolution study examined trade‐off between showed could be resolved for regions with good ray path...

Ambient noise tomography is applied to the significant data resources now available across Tibet and surrounding regions produce Rayleigh wave phase speed maps at periods between 6 50 s. Data include permanent Federation of Digital Seismographic Networks, five temporary U.S. Program for Array Seismic Studies Continental Lithosphere (PASSCAL) experiments in around Tibet, Chinese provincial networks from 2003 2009, totaling ∼600 stations ∼150,000 interstation paths. With such a heterogeneous...

SUMMARY Tomographic imaging of the uppermost mantle velocity in Middle East shows normal Pn velocities (8.0-8.2 kms-’) beneath Black Sea and southern Caspian Sea. In contrast, low (<7.9 km s-I) are found Aegean much Turkish-Iranian Plateau. A region exceptionally (c7.6 s-’) Lesser Caucasus Mountains along border coincides with a high Sn attenuation extensive Neogene volcanism. All these features suggest that near solidus conditions exist within Such may result either from decompression...

SKS and SKKS shear waves recorded on the INDEPTH III seismic array deployed in central Tibet during 1998–1999 have been analyzed for direction extent of polarization anisotropy. The 400‐km‐long NNW trending extended south to north, from Lhasa terrane, across Karakoram‐Jiali fault system Banggong‐Nujiang suture Qiangtang terrane. Substantial splitting with delay times 1 2 s, fast directions varying E‐W NE‐SW, was observed stations terrane northernmost No detectable located farther change wave...

In the summer of 1998, project INDEPTH recorded a 400 km long NNW–SSE wide-angle seismic profile in central Tibet, from Lhasa terrane across Banggong-Nujiang suture (BNS) at about 89.5°E and into Qiangtang terrane. Analysis P-wave data reveals that (1) crustal thickness is 65 ± 5 beneath line; (2) there no 20 step Moho vicinity BNS, as has been suggested to exist along-strike east based on prior fan profiling; (3) thick high-velocity lower layer evident along length (20–35 thick, 6.5–7.3...

Seismic P wave velocity variations in the uppermost mantle beneath China are tomographically imaged using Pn travel time data. The average of lid is 8.05 km/s, with a range from −0.30 km/s to 0.35 km/s. Eastern has slower velocities and thinner crust than western China. Different inversions performed for shorter ray path longer data sets separated shallow deep structure within lid. Velocities lower no more 0.2 faster at top. fastest cratons, which remained relatively undeformed despite...

abstract A tomographic inversion of the Pn arrivals in Southern California yields new information about wave velocities and topography on Moho discontinuity. We produce maps velocity station delays. The do not show dramatic correlation with surface faults that is found for shallower Pg (Hearn Clayton, 1986). This implies lower crust mantle are largely decoupled from upper crust. Undoubtedly, this due to different responses brittle ductile tectonic isostatic stresses. Detachment must play an...

The Pn arrivals recorded from the southern California array have been used to demonstrate regional variations in crustal thickness and velocity investigate presence of anisotropy mantle. Over 2800 travel times were analysis. classical time term method was extended allow Moho vary a block‐type structure. statistical F test shows these effects be significant. Crustal delays determined depend on both velocities depth. Ventura Los Angeles basins sediment which indicate thicknesses near 10 km....

We use receiver functions calculated for data collected by the INDEPTH‐IV seismic array to image three‐dimensional geometry of crustal and upper mantle velocity discontinuities beneath northeastern Tibet. Our results indicate an average thickness 65 70 km in northern In addition, we observe a 20 Moho offset margin Kunlun Mountains, 10 across Jinsha River Suture gently northward dipping Qaidam Basin. A region central Qiangtang Terrane with higher than normal Vp/Vs ratio ∼1.83 can be result...

Shear wave splitting measurements using teleseismic SKS and SKKS phases recorded by the INDEPTH‐IV arrays has revealed a strong upper mantle anisotropic fabric in northeastern Tibet with large delay times of up to 2.2 s, suggesting that anisotropy exists both lithospheric asthenospheric mantle. The coherence among fast polarization orientations split core left‐lateral slip on eastern‐striking, southern‐striking faults eastern surface deformation fields calculated from GPS observations...

Abstract We present propagation characteristics of the short-period regional seismic phases Sn and Lg for Middle East. Digital waveform data from Iranian Long Period Array (ILPA) Global Seismic Network (GSN) stations ABKT (Alibek, Turkmenistan), ANTO (Ankara, Turkey), KEG (Kottamya, Egypt), KIV (Kislovodsk, Georgia) were used in this study. Three-component rotated seismograms bandpass filtered (0.5 to 5.0 Hz) examined presence strength (amplitude) relative Pn Pg phases. The waveforms show...

Pn data collected within southern Europe and the Mediterranean are used to tomographically image variations in both seismic velocity anisotropy. Seismic anisotropy is an essential part of inversion, without it, several low features uppermost mantle could not be properly imaged. The technically active has much lower velocities (7.6–8.1 km/s) than more stable sub‐African plate Adriatic sea (8.3 km/s). However, most dramatic Europe's relate Apennine, Dinaride, Hellenide arcs. These arcs all...

This paper presents the results of a joint Lithoprobe‐Incorporated Research Institutions for Seismology (IRIS)/Program Array Seismic Studies Continental Lithosphere (PASSCAL) teleseismic experiment that investigates portions Grenville and Superior Provinces Canadian Shield along Québec‐Ontario border. Data from 600‐km‐long, N‐S array 28 broadband seismographs deployed between May October 1996 have been supplemented with additional recordings an earlier 1994 deployment stations National...

First arrival times from regional distances (200–1200 km) in the western United States extracted International Seismological Centre (ISC) data set were inverted a tomographic study to map laterally varying Pn velocity structure of uppermost mantle (i.e., lid) and estimate crustal static delay at each seismograph station. Synthetic used evaluate resolution. Results correlate well with major tectonic features. We find low velocities (V &lt; 7.9 km/s) centered Basin Range Province surrounded by...

[1] The Q of regional seismic phases Lg and Pg within the crust is assumed as a proxy for crustal Qβ Qα, which used constraint rheology. We measure regional-phase eastern Tibetan Plateau adjacent areas. This method eliminates contributions from source site responses an improvement on Two-Station Method (TSM). have generated tomographic images attenuation anomalies with resolution high 1°. In general we observe low in northernmost portions more tectonically stable regions such interior Qaidam...

Aftershocks of the 29 November 1978 Oaxaca, Mexico, earthquake (surface-wave magnitude Ms = 7.8) define a rupture area about 6000 square kilometers along boundary Cocos sea-plate subduction. This had not ruptured in large (Ms >/= 7), shallow since years 1928 and 1931 been designated seismic "gap." The region has also seismically quiet for small to moderate (M 4), (depth </= 60 kilometers) earthquakes 1966; this zone became six times larger 1973. A major 7.5 +/- 0.25) was forecast at location...

Travel times of about 39,000 Pn arrivals recorded from regional earthquakes by the Italian Telemetered Seismic Network and stations nearby countries are inverted to image lateral variations seismic velocity anisotropy at subcrustal depth in Italy surrounding regions. This method allows simultaneous imaging anisotropy, as well crustal thickness variations. The Po plain, Adriatic Sea, Ionian Sea have normal high velocities. In contrast, lower velocities (7.9–8.0 km/s) imaged beneath western...

Relict sutures from colliding continents, regions characterized by a 'young' Moho, layering and faulting throughout the crust, mid-crustal magma traps, seismic 'bright spots' which suggest deep crustal fluids are among recent COCORP findings. In addition, new studies of signal penetration, noise mitigation, recording geometry, coherency filtering have yielded better understanding of, substantial improvements in, data quality. Amplitude anomalies, or spots', in Basin Range may be due to at...

Abstract We have developed a bootstrap method to estimate errors associated with inverting SKS waveforms for shear-wave splitting parameters. Although presented inversions, this is suitable any waveform inversion procedure. The error estimation consists of multiple inversions simulated data that imitate the original differing noise sequences. results are used directly calculate variances and covariances all model employ technique nonlinear Since seismic correlated errors, was modified...

A total of 400 regional earthquakes were located in northern Tibetan Plateau from data recorded by INDEPTH‐IV and PKU Eastern Kunlun arrays May 2007 to June 2009. The distribution these is compatible with a continuously deforming lithosphere. Most occur at depth range 0‐15 km, but no event deeper than 30 km. This observation strongly supports the existence hot weak lower crust beneath Tibet. crustal seismogenic zone appears slightly thicker Tibet southern plateau, possibly reflecting...

Using Pn-wave traveltimes from three regional distance ranges we generated Pn tomography models to investigate the 3-D nature of uppermost mantle lid P-wave velocity structure beneath Tibetan Plateau and surrounding regions. Significant variations spatially with depth are observed. High-velocity regions found Himalayas most parts southern Tibet. These high-velocity can be interpreted as subducting Indian continental lithosphere, accreted terranes a cold, non-convective wedge central Plateau....

Abstract A comprehensive study of the gross characteristics high-frequency seismic-wave propagation in China and its surrounding regions was accomplished to learn more about how regional geology affects phases. Amplitudes seismic waves Sn Lg relative P coda were used map lateral variations shear-wave attenuation crust upper mantle. Over 7000 digital seismograms from 13 broadband stations Chinese Digital Seismic Network Global frequency range 0.5 5.0 Hz visually examined. Propagation...

Amplitude tomography reconstructs seismic attenuation directly from recorded wave amplitudes. We have applied the to amplitude data reported in 'Annual Bulletin of Chinese Earthquakes' and interpreted regionally varying crustal terms tectonics. The amplitudes were originally for determining ML MS magnitudes. They generally correspond maximum horizontal components short-period S waves intermediate-period Rayleigh waves. Both sets measurements are sensitive structure. peak spread spherically...