Remnants of the Amalgamation of the East and West Cathaysia Blocks Revealed by a Short-period Dense Seismic Array

2022 ◽  
Author(s):  
He Huang ◽  
Xuzhang Shen ◽  
Jian Xu ◽  
Rui Gao ◽  
Wentian Wang ◽  
...  
Keyword(s):  
Seismic Array ◽  
Short Period ◽  
East And West ◽  
Dense Seismic Array

Investigating the crustal reflections of Taiwan from autocorrelation of seismic noise

2020 ◽  
Author(s):  
Zhuo-Kang Guan ◽  
Hao Kuo-Chen
Keyword(s):  
Receiver Function ◽  
Velocity Model ◽  
Seismic Array ◽  
Recording Time ◽  
Near Surface ◽  
Seismic Arrays ◽  
Short Period ◽  
Cross Correlations ◽  
Moho Depths ◽  
Dense Seismic Array

<p><span>Seismic interferometry is widely applied in various scales to reconstruct seismic signals for investigating Earth interior. The method of Phase Cross Correlation (PCC) takes less pre-processing and is more stable for retrieving of crustal signals than that of the conventional cross correlations by using amplitude information. In order to obtain the crustal reflectors in Taiwan, we applied auto-correlation with PCC to two independent datasets, (1) temporary seismic array in eastern Taiwan with 110 short period seismometers and (2) broadband seismic arrays (BATS and TAIGER) in Taiwan. As a result, the retrieved crustal reflectors, such as Moho reflectors, are stable with different recording time periods and instruments: temporal and spatial signal consistencies in the same site and neighborhood stations, respectively, and also high waveform similarities between short period and broadband seismometers.</span></p><p><span>Comparing the results with previous studies of velocity model and receiver function, the reflections at 10-12 seconds (roughly 30-40 km) are often observed in most of the results which are correlated to the Moho depths inferred from the receiver function and tomography studies. It is interesting to note that, besides the Moho reflections, some inter-crustal reflectors beneath the Central Range are revealed. The results show that the autocorrelation method has the potential to investigate some signals that are difficult to observe in the past by using other methods.</span></p><p><span>Another interesting observation from a dense seismic array in eastern Taiwan shows that the chimei fault serves as a sharp boundary to separate the reflectional signals into the northern and southern parts. In the southern part few reflections can be observed and also lack high frequency energies from autocorrelation comparing with those in the northern part. It implies that the distribution of ambient sources or near surface materials could influence the results. After examining the PCC’s feasibility and stability in this study, it is necessary to verify the reliability of results by understanding the source’s properties and local geological situations before interpretation.</span></p>

Integrated geophysical data for investigating the tectonic structures in eastern Taiwan

2020 ◽  
Author(s):  
Hao Kuo-Chen ◽  
Zhuo-Kang Guan ◽  
Wei-Fang Sun ◽  
Chun-Rong Chen
Keyword(s):  
Seismic Reflection ◽  
Plate Boundary ◽  
Seismic Array ◽  
Magnetic Survey ◽  
Eurasian Plate ◽  
Tectonic Structures ◽  
Sedimentary Deposits ◽  
Aftershock Sequences ◽  
Short Period ◽  
Dense Seismic Array

<p>The Taiwan orogeny is forming along a complex plate boundary in which the Eurasian Plate (EUP) is subducting eastward beneath the Philippine Sea Plate (PSP). This complex plate boundary is situated in eastern Taiwan and results in large earthquakes occurred frequently in this region. For instance, in 1951, 1972, 1986, 2003, 2006, 2013, 2018, and 2019, earthquakes with magnitude greater than 6 occurred near or along the plate boundary and most of them caused serious damages. However, due to the complexity of the plate boundary from south to north of eastern Taiwan, the seismogenic structures for those events are very different. In order to understand the tectonic structures thoroughly in eastern Taiwan, we planned a integrated geophysical experiment, including seismic reflection, dense seismic array deployments, and magnetic survey from 2016 to 2020. There are 8 seismic reflection profiles along the Longitudinal valley from north to south. As a result, the seismic images show that the sedimentary deposits can reach ~1 km thickness in the northern part and is shallower toward to the southern part. The rocks below the sedimentary deposits are from the east flank of the Longitudinal valley, which belongs to the Eurasian plate. The dense array deployments from 2016-2019 around eastern Taiwan with 1-5 km spacing and totally more than 300 short-period stations deployed. During the deployments, we have captured two aftershock sequences in the north of eastern Taiwan in 2018 and 2019. The seismogenic zones with high-resolution tomography from dense seismic array data sets reveal that the plate interaction between the EUP and PSP. The physical behaviors of the seismogenic zones are related to the collision to subduction along the plate boundary from south to north. Also, the results of the magnetic survey in eastern Taiwan show that the high magnetic anomalies only sparsely distribute, which indicates the volcanic arc may not widely occupy than previous geological investigation. The results of this experiment provide a new thought of the tectonic processes along the plate boundary in eastern Taiwan.</p>

Cenozoic magmatic activity and oblique uplifting of the Ailao Mountain: Evidence from a short-period dense seismic array

2020 ◽  
Vol 63 (9) ◽  
pp. 1294-1308
Author(s):  
Lu Zhang ◽  
Zhiming Bai ◽  
Tao Xu ◽  
Zhenbo Wu ◽  
Minfu Huang ◽  
...  
Keyword(s):  
Seismic Array ◽  
Magmatic Activity ◽  
Short Period ◽  
Dense Seismic Array ◽  
Ailao Mountain

P-wave backazimuth anomalies observed by a small-aperture seismic array at Pinyon Flat, southern California: Implications for structure and source location

1996 ◽  
Vol 86 (2) ◽  
pp. 470-476 ◽  
Author(s):  
Cheng-Horng Lin ◽  
S. W. Roecker
Keyword(s):  
Southern California ◽  
Seismic Array ◽  
P Wave ◽  
Small Aperture ◽  
Data Set ◽  
Single Interface ◽  
Seismic Networks ◽  
Dense Seismic Array ◽  
Beamforming Technique

Abstract Seismograms of earthquakes and explosions recorded at local, regional, and teleseismic distances by a small-aperture, dense seismic array located on Pinyon Flat, in southern California, reveal large (±15°) backazimuth anomalies. We investigate the causes and implications of these anomalies by first comparing the effectiveness of estimating backazimuth with an array using three different techniques: the broadband frequency-wavenumber (BBFK) technique, the polarization technique, and the beamforming technique. While each technique provided nearly the same direction as a most likely estimate, the beamforming estimate was associated with the smallest uncertainties. Backazimuth anomalies were then calculated for the entire data set by comparing the results from beamforming with backazimuths derived from earthquake locations reported by the Anza and Caltech seismic networks and the Preliminary Determination of Epicenters (PDE) Bulletin. These backazimuth anomalies have a simple sinelike dependence on azimuth, with the largest anomalies observed from the southeast and northwest directions. Such a trend may be explained as the effect of one or more interfaces dipping to the northeast beneath the array. A best-fit model of a single interface has a dip and strike of 20° and 315°, respectively, and a velocity contrast of 0.82 km/sec. Application of corrections computed from this simple model to ray directions significantly improves locations at all distances and directions, suggesting that this is an upper crustal feature. We confirm that knowledge of local structure can be very important for earthquake location by an array but also show that corrections computed from simple models may not only be adequate but superior to those determined by raytracing through smoothed laterally varying models.

scholarly journals Basic data features and results from a spatially dense seismic array on the San Jacinto fault zone

2015 ◽  
Vol 202 (1) ◽  
pp. 370-380 ◽  
Author(s):  
Yehuda Ben-Zion ◽  
Frank L. Vernon ◽  
Yaman Ozakin ◽  
Dimitri Zigone ◽  
Zachary E. Ross ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Array ◽  
Basic Data ◽  
San Jacinto Fault ◽  
San Jacinto Fault Zone ◽  
Dense Seismic Array

Estimation of Direction of Wavefront Propagation and Slowness Using Time Domain Wavenumber Analysis in Small-Size Dense Seismic Arrays

2012 ◽  
Vol 479-481 ◽  
pp. 1186-1189
Author(s):  
Ping Liu ◽  
Hua Ma ◽  
Xue Wei Zhang ◽  
Xin Yu Sun ◽  
Fei Cao
Keyword(s):  
Time Domain ◽  
Seismic Array ◽  
Apparent Velocity ◽  
Seismic Signals ◽  
Analysis Method ◽  
Seismic Arrays ◽  
Wavefront Propagation ◽  
Pass Through ◽  
The Time Domain ◽  
Dense Seismic Array

The time domain wavenumber analysis method can directly delay and align signals before the superposition of signals in the time domain. In this paper, estimating the direction of wavefront propagation and the slowness for seismic signals which pass through the small-size dense seismic array is described in detail. The earthquake recorder sample adopted from US Geological Survey Parkfield Dense Seismograph Array (UPSAR array) of the U.S is used for analyzing. The results indicate that, the direction of wavefront propagation cannot be determined rashly only by the connecting line of the earthquake epicenter to the seismic array. The accuracy of the apparent velocity and the direction of wavefront propagation calculated using vertical seismic recorders is higher in West-East direction and in North-South direction.

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