Spatial Distribution of Radiated Seismic Energy from Local and Regional Earthquakes in Taiwan

2020 ◽  
Author(s):  
Himanshu Mittal ◽  
Ting-Li Lin ◽  
Yun-Hsuan Huang
Keyword(s):  
Spatial Distribution ◽  
Energy Release ◽  
Lower Crust ◽  
Driving Forces ◽  
Seismic Energy ◽  
Energy Calculation ◽  
Detailed Knowledge ◽  
Upper Crust ◽  
Ryukyu Trench ◽  
Released Energy

<p>The radiated energy during earthquakes is one of the important characteristics that have a great impact on human lives. The study of the released energy during earthquakes and their distribution may provide a detailed knowledge about the driving forces. The earthquakes occurring between 1994 and 2018 are used to study the spatial distribution of energy in and around Taiwan. The maximum depth of earthquakes used in the present work is 320 km. Hwang's (2012) approach based on local records from Taiwan is used to estimate energy for all earthquakes having  M<sub>L</sub> ≤ 6.4. As  M<sub>L</sub> saturates for higher magnitude earthquakes, a correction factor is applied to all earthquakes above 6.4 based on energy calculation for Chi-Chi and JiaSian earthquake. It is found that the distribution of earthquake numbers and energy is not uniform. In particular, 99% of the events occurred within 100 km while the remaining 1% occurred from 100 to 320 km. Most of the events, about 78% of the total earthquakes are confined to the upper 20 km depth. Around 90% of energy release in and around Taiwan is contributed by the earthquakes occurring to a depth of 100 km. Only a few earthquakes occur beyond 100 km depth; contributing around 10% of total released energy. The highest energy release is attributed to the eastern subduction along the Ryukyu trench. Our results show that the lower crust may play an important role in energy distribution, though most of the earthquakes have occurred in the upper crust.  So, in addition to upper crust controlling plate-driving forces, the lower crust may also control these forces causing deformation. Therefore, the temporal and spatial distributions of seismic energy release can be further studied to reveal the characteristics of the seismogenic zone in the future.</p><p>Keywords: Energy, Magnitude, Subduction, Ryukyu trench, Subduction</p><p></p>

scholarly journals Spatio-temporal distribution patterns of Plutella xylostella (Lepidoptera: Plutellidae) in a fine-scale agricultural landscape based on geostatistical analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jian-Yu Li ◽  
Yan-Ting Chen ◽  
Meng-Zhu Shi ◽  
Jian-Wei Li ◽  
Rui-Bin Xu ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Plutella Xylostella ◽  
Agricultural Landscape ◽  
Seasonal Pattern ◽  
Distribution Patterns ◽  
Geostatistical Analysis ◽  
Distribution Model ◽  
Detailed Knowledge ◽  
Fine Scale ◽  
Spatio Temporal

AbstractA detailed knowledge on the spatial distribution of pests is crucial for predicting population outbreaks or developing control strategies and sustainable management plans. The diamondback moth, Plutella xylostella, is one of the most destructive pests of cruciferous crops worldwide. Despite the abundant research on the species’s ecology, little is known about the spatio-temporal pattern of P. xylostella in an agricultural landscape. Therefore, in this study, the spatial distribution of P. xylostella was characterized to assess the effect of landscape elements in a fine-scale agricultural landscape by geostatistical analysis. The P. xylostella adults captured by pheromone-baited traps showed a seasonal pattern of population fluctuation from October 2015 to September 2017, with a marked peak in spring, suggesting that mild temperatures, 15–25 °C, are favorable for P. xylostella. Geostatistics (GS) correlograms fitted with spherical and Gaussian models showed an aggregated distribution in 21 of the 47 cases interpolation contour maps. This result highlighted that spatial distribution of P. xylostella was not limited to the Brassica vegetable field, but presence was the highest there. Nevertheless, population aggregations also showed a seasonal variation associated with the growing stage of host plants. GS model analysis showed higher abundances in cruciferous fields than in any other patches of the landscape, indicating a strong host plant dependency. We demonstrate that Brassica vegetables distribution and growth stage, have dominant impacts on the spatial distribution of P. xylostella in a fine-scale landscape. This work clarified the spatio-temporal dynamic and distribution patterns of P. xylostella in an agricultural landscape, and the distribution model developed by geostatistical analysis can provide a scientific basis for precise targeting and localized control of P. xylostella.

scholarly journals Effect of W on the Impact-Induced Energy Release Behavior of Al–Ni Energetic Structural Materials

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1217
Author(s):  
Shun Li ◽  
Caimin Huang ◽  
Jin Chen ◽  
Yu Tang ◽  
Shuxin Bai
Keyword(s):  
Energy Release ◽  
Structural Materials ◽  
Damage Effect ◽  
Hot Press ◽  
Reaction Heat ◽  
Metal Metal ◽  
Energetic Structural Materials ◽  
Released Energy ◽  
The Impact ◽  
Hot Press Process

Energetic structural materials (ESMs) are an important class of military materials due to their good structural and energy-releasing characteristics. To improve the damage effect of metal–metal ESMs with good mechanical properties, W was added to the 48Al–52Ni composites, and the effect of W on the impact-induced energy release behaviors was investigated. The results showed that the hot-press process and the addition of W did not change the microstructure and surface state of the constituent particles, leading to a stable onset temperature of the Al–Ni intermetallic reaction in (48Al–52Ni)100-xWx composites. Meanwhile, the decrease in the contact area between Al and Ni in the composites with increased W content resulted in the decrease in reaction heat. During the impact process, the intermetallic reaction of W caused by the Al–Ni intermetallic reaction, as well as the oxidation reaction of Al and Ni caused by the brittle fracture along the weak interface, caused the released energy of (48Al–52Ni)40W60 to reach 2.04 kJ/g.

Results of a seismic reflection survey across the fault zone between the Thompson nickel belt and the Churchill Tectonic Province, northern Manitoba

1981 ◽  
Vol 18 (1) ◽  
pp. 13-25 ◽  
Author(s):  
A. G. Green
Keyword(s):  
Fault Zone ◽  
Lower Crust ◽  
Seismic Reflection ◽  
High Amplitude ◽  
Small Scale ◽  
Upper Crust ◽  
Travel Times ◽  
Reflection Point ◽  
Point Data ◽  
Amplitude Reflection

Approximately 11 km of four-fold common reflection point data have been recorded across a region that spans the contact fault zone between the Thompson nickel belt and the Churchill Tectonic Province. From these data it is shown that the upper crust in this region and, to a lesser extent, the lower crust are characterized by numerous scattered events that originate from relatively small-scale features. Within the Thompson nickel belt two extensive and particularly high-amplitude reflection zones, at two-way travel times of t = 5.0–5.5 s and t = 6.0–6.5 s, are recorded with apparent northwesterly dips of 0–20 °C. These reflection zones, which have a laminated character, are truncated close to the faulted contact with the Churchill Province. Both the contact fault zone and the Churchill Province in this region have crustal sections that are relatively devoid of significant reflectors. The evidence presented here confirms that the crustal section of the Thompson nickel belt is fundamentally different from that of the Churchill Tectonic Province.

Dynamics of the extension in the Fonualei Rift in the northern Lau Basin at 16 °S

2021 ◽  
Author(s):  
Anna Jegen ◽  
Anke Dannowski ◽  
Heidrun Kopp ◽  
Udo Barckhausen ◽  
Ingo Heyde ◽  
...  
Keyword(s):  
Velocity Gradient ◽  
Lower Crust ◽  
Pacific Plate ◽  
P Wave ◽  
Upper Crust ◽  
Lau Basin ◽  
Australian Plate ◽  
The Pacific ◽  
Refraction Seismic ◽  
Roll Back

<p>The Lau Basin is a young back-arc basin steadily forming at the Indo-Australian-Pacific plate boundary, where the Pacific plate is subducting underneath the Australian plate along the Tonga-Kermadec island arc. Roughly 25 Ma ago, roll-back of the Kermadec-Tonga subduction zone commenced, which lead to break up of the overriding plate and thus the formation of the western Lau Ridge and the eastern Tonga Ridge separated by the emerging Lau Basin.</p><p>As an analogue to the asymmetric roll back of the Pacific plate, the divergence rates decline southwards hence dictating an asymmetric, V-shaped basin opening. Further, the decentralisation of the extensional motion over 11 distinct spreading centres and zones of active rifting has led to the formation of a composite crust formed of a microplate mosaic. A simplified three plate model of the Lau Basin comprises the Tonga plate, the Australian plate and the Niuafo'ou microplate. The northeastern boundary of the Niuafo'ou microplate is given by two overlapping spreading centres (OLSC), the southern tip of the eastern axis of the Mangatolu Triple Junction (MTJ-S) and the northern tip of the Fonualei Rift spreading centre (FRSC) on the eastern side. Slow to ultraslow divergence rates were identified along the FRSC (8-32 mm/a) and slow divergence at the MTJ (27-32 mm/a), both decreasing southwards. However, the manner of divergence has not yet been identified. Additional regional geophysical data are necessary to overcome this gap of knowledge.</p><p>Research vessel RV Sonne (cruise SO267) set out to conduct seismic refraction and wide-angle reflection data along a 185 km long transect crossing the Lau Basin at ~16 °S from the Tonga arc in the east, the overlapping spreading centres, FRSC1 and MTJ-S2, and extending as far as a volcanic ridge in the west. The refraction seismic profile consisted of 30 ocean bottom seismometers. Additionally, 2D MCS reflection seismic data as well as magnetic and gravimetric data were acquired.</p><p>The results of our P-wave traveltime tomography show a crust that varies between 4.5-6 km in thickness. Underneath the OLSC the upper crust is 2-2.5 km thick and the lower crust 2-2.5 km thick. The velocity gradients of the upper and lower crust differ significantly from tomographic models of magmatically dominated oceanic ridges. Compared to such magmatically dominated ridges, our final P-wave velocity model displays a decreased velocity gradient in the upper crust and an increased velocity gradient in the lower crust more comparable to tectonically dominated rifts with a sparse magmatic budget.</p><p>The dominance of crustal stretching in the regional rifting process leads to a tectonical stretching, thus thinning of the crust under the OLSC and therefore increasing the lower crust’s velocity gradient. Due to the limited magmatic budget of the area, neither the magnetic anomaly nor the gravity data indicate a magmatically dominated spreading centre. We conclude that extension in the Lau Basin at the OLSC at 16 °S is dominated by extensional processes with little magmatism, which is supported by the distribution of seismic events concentrated at the northern tip of the FRSC.</p>

Spatial distribution and origin of the high-velocity lower crust in the northeastern South China Sea

2021 ◽  
pp. 229086
Author(s):  
Jinhui Cheng ◽  
Jiazheng Zhang ◽  
Minghui Zhao ◽  
Feng Du ◽  
Chaoyan Fan ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
South China Sea ◽  
South China ◽  
High Velocity ◽  
Lower Crust ◽  
China Sea ◽  
Northeastern South China Sea

An application of a stochastic model to a volcanic earthquake swarm

1975 ◽  
Vol 65 (2) ◽  
pp. 351-357
Author(s):  
John Filson ◽  
Tom Simkin
Keyword(s):  
Stochastic Model ◽  
Energy Release ◽  
Earthquake Swarm ◽  
Seismic Energy ◽  
Volcanic Earthquake ◽  
Model Studies ◽  
Seismic Energy Release ◽  
Earthquake Model ◽  
Event Occurrence

abstract The Kolomogorov model of event occurrence as developed by Knopoff in earthquake model studies has been applied to a volcanic earthquake swarm. It is shown that in this case, where the rate of seismic energy release was nearly constant in time, the model adequately relates the various seismicity statistics of the swarm.

Thermodynamic constraints on assimilation of silicic crust by primitive magmas

2021 ◽  
Author(s):  
Jussi S Heinonen ◽  
Frank J Spera ◽  
Wendy A Bohrson
Keyword(s):  
Phase Equilibria ◽  
Lower Crust ◽  
Primitive Mantle ◽  
Upper Crust ◽  
Basaltic Composition ◽  
Primitive Magma ◽  
Partial Melts ◽  
Thermodynamic Limits ◽  
Melt Composition ◽  
Lower Crustal

<p>Some studies on basaltic and more primitive rocks suggest that their parental magmas have assimilated more than 50 wt.% (relative to the initial uncontaminated magma) of crustal silicate wallrock. But what are the thermodynamic limits for assimilation by primitive magmas? This question has been considered for over a century, first by N.L. Bowen and many others since then. Here we pursue this question quantitatively using a freely available thermodynamic tool for phase equilibria modeling of open magmatic systems — the Magma Chamber Simulator (MCS; https://mcs.geol.ucsb.edu).</p><p>In the models, komatiitic, picritic, and basaltic magmas of various ages and from different tectonic settings assimilate progressive partial melts of average lower, middle, and upper crust. In order to pursue the maximum limits of assimilation constrained by phase equilibria and energetics, the mass of wallrock in the simulations was set at twice that of the initially pristine primitive magmas. In addition, the initial temperature of wallrock was set close to its solidus at a given pressure. Such conditions would approximate a rift setting with tabular chambers and high magma input causing concomitant crustal heating and steep geotherms.</p><p>Our results indicate that it is difficult for any primitive magma to assimilate more than 20−30 wt.% of upper crust before evolving to intermediate/felsic compositions. However, if assimilant is lower crust, typical komatiitic magmas can assimilate more than their own weight (range of 59−102 wt.%) and retain a basaltic composition. Even picritic magmas, more relevant to modern intraplate settings, have a thermodynamic potential to assimilate 28−49 wt.% of lower crust before evolving into intermediate/felsic compositions.</p><p>These findings have important implications for petrogenesis of magmas. The parental melt composition and the assimilant heavily influence both how much assimilation is energetically possible in primitive magmas and the final magma composition. The fact that primitive mantle melts have potential to partially melt and assimilate significant fractions of (lower) crust may have fundamental importance for how trans-Moho magmatic systems evolve and how crustal growth is accomplished. Examples include generation of siliceous high-magnesium basalts in the Precambrian and anorogenic anorthosite-mangerite-charnockite-granite complexes with geochemical evidence of considerable geochemical overprint from (lower) crustal sources.</p>

How seismicity relates to lithospheric heterogeneity in the Alps

2021 ◽  
Author(s):  
Ajay Kumar ◽  
Cameron Spooner ◽  
Magdalena Scheck-Wenderoth ◽  
Mauro Cacace
Keyword(s):  
Lower Crust ◽  
Convergence Rates ◽  
Upper Rhine Graben ◽  
Topographic Effects ◽  
Relative Role ◽  
Upper Crust ◽  
Radiogenic Heat ◽  
First Order ◽  
Tectonic Inheritance ◽  
The Alps

<p>The Alps mountains and its forelands consist of a heterogeneous lithosphere, comprised of a multitude of tectonic blocks from different tectonic provinces with different thermo-physical properties. Patterns of seismicity distribution are also observed to vary significantly throughout the region. However, the relationship between seismicity and lithospheric heterogeneity has been often overlooked in previous studies. We present an overview of recent results that have attempted to address these questions through the use of integrated 3D modelling techniques, thereby including: (i) a gravity and seismic data constrained, 3D, density structural model of the lithosphere; (ii) a 3D thermal model constrained against available wellbore temperature data; and,  (iii) a 3D rheological model of the long-term lithospheric strength and effective viscosities. Our models support the existence of a first-order correlation between the distribution of seismicity (laterally and with depth) and the strength of the lithosphere, with the former being clustered mainly within weaker domains. Beneath the Alps, observed upper-crustal level (i.e., unimodal) seismicity correlates with a weaker lithosphere where plate strength is controlled by the thick crustal root. Whereas in the southern foreland, weaker zones are found preferentially around the stronger Adriatic indenter while in the northern foreland they are located in the crust beneath the the Upper Rhine Graben (URG). We found that this correlation is primarily controlled by resolved thermal gradients and is a function of the tectonic inheritance setting (e.g., UGR), crustal architecture (e.g., thickness of sediments, upper and lower crust) and LAB depth. Sediment thickness and topographic effects controls the shallow thermal filed (0 – 10 km) whereas the deeper thermal field is controlled by the thickness of felsic upper crust (higher radiogenic heat contribution), the mafic lower crust (less radiogenic heat contribution) and basal thermal boundary condition from LAB depth. Seismicity is bounded by specific isotherms, 450 <sup>o</sup>C in the crust and < 600 <sup>o</sup>C in the mantle, except in regions where slabs are imaged by seismic tomography models. This is in contrast to the recent proposition that convergence velocity is a first-order factor controlling seismicity in an orogen rather than its architecture. Fast convergence rates (e.g., Himalayas) have been related to the subduction of the cold crust to deeper crustal depths thereby leading to a deepening of the brittle  domain and to a bimodal (i.e., upper and lower crust) seismicity character. In contrast, slow convergence (e.g., Alps) is thought to lead to a hotter ductile lower crust thus limiting brittle deformation within the upper crust. We therefore end our contribution by opening a discussion on the relative role of convergence rates and lithospheric heterogeneities, inherited and/or developed during orogenesis, in controlling the seismicity. In doing so we carry out a comparison between observed seismicity and lithospheric architecture in the other mountain ranges of the western Alpine-Himalayan collision zone where  convergence velocities are of a similar order of magnitudes as Alps, i.e., the Betics, the Pyrenees and the Apennines but where seismicity is observed to occur both at upper and lower crustal levels.</p>

scholarly journals Evaluation of crustal inhomogeneity parameters in the southern Longmenshan fault zone and adjacent regions

2020 ◽  
Vol 24 (6) ◽  
pp. 1175-1188
Author(s):  
Xiao-Ping Fan ◽  
Yi-Cheng He ◽  
Cong-Jie Yang ◽  
Jun-Fei Wang
Keyword(s):  
Fault Zone ◽  
Lower Crust ◽  
Tectonic Deformation ◽  
Upper Crust ◽  
Crust And Upper Mantle ◽  
Study Region ◽  
Waveform Data ◽  
Longmenshan Fault Zone ◽  
Deformation Features ◽  
Longmenshan Fault

AbstractBroadband teleseismic waveform data from 13 earthquakes recorded by 70 digital seismic stations were selected to evaluate the inhomogeneity parameters of the crustal medium in the southern Longmenshan fault zone and its adjacent regions using the teleseismic fluctuation wavefield method. Results show that a strong inhomogeneity exists beneath the study region, which can be divided into three blocks according to its structure and tectonic deformation features. These are known as the Sichuan-Qinghai Block, the Sichuan-Yunnan Block, and the Mid-Sichuan Block. The velocity fluctuation ratios of the three blocks are approximately 5.1%, 3.6%, and 5.1% in the upper crust and 5.1%, 3.8%, and 4.9% in the lower crust. The inhomogeneity correlation lengths of the three blocks are about 10.1 km, 14.0 km, and 10.7 km in the upper crust and 11.8 km, 17.0 km, and 11.8 km in the lower crust. The differences in the crustal medium inhomogeneity beneath the Sichuan-Yunnan Block, the Sichuan-Qinghai Block, and the Mid-Sichuan Block may be related to intensive tectonic movement and material flow in the crust and upper mantle.

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