Zone Head Research Articles

Bimaterial interfaces in the south San Andreas Fault with opposite velocity contrasts NW and SE from San Gorgonio Pass

AbstractAnalysis of fault zone head waves indicates the existence of two deep large‐scale bimaterial interfaces in the structure of the southern San Andreas Fault (SAF) with opposite sense of velocity contrast. One interface extends from the Cajon Pass area to the San Gorgonio Pass (SGP) region and is associated with a slower seismic velocity on the southwest side of the SAF. The second interface extends from the SGP region to the Coachella Valley and involves a slower seismic velocity on the northeast side. Tomographic imaging of alternating velocity structures supports the velocity contrast reversal across the SAF. The observations and expected properties of bimaterial ruptures suggest that earthquakes nucleating slightly to the NW and SE of SGP tend to propagate along the SAF in the opposite along‐strike directions. This is consistent with geological and seismological evidence in the Mojave and southernmost sections of the SAF.

A Novel Approach For Elect A Zone Head On The Basis Of Energy and Distance of Base Station In WSN

Performance estimation is a most important study part in WSN and a prosperity of literature exists in this area. IN WSN, DOS attacks are known as threats that is an extremely serious threat due to the resources feature. Applications of the WSNs are transitioning to real-world, where they face attacks already skilled through the WAN and Internet. DOS is one form of attacks, which we will believe only become large common as accessible and sensor networks. WSN devices include limitations of the inherent resource, they are most receptive to the consumption and laying waste of these weak resources. In this paper on the basis of energy and distance of base station elect a zone head. The simulation of the proposed work concludes that the results of the approach are good it provides better results in terms of throughput and packet delivery ratio.

Automatic identification of fault zone head waves and directPwaves and its application in the Parkfield section of the San Andreas Fault, California

Automatic identification of fault zone head waves and direct<i>P</i>waves and its application in the Parkfield section of the San Andreas Fault, California

Bimaterial interfaces at the Karadere segment of the North Anatolian Fault, northwestern Turkey

AbstractWe image velocity contrast (bimaterial) interfaces along the Karadere Fault of the North Anatolian Fault Zone, toward the eastern part of the 1999 Izmit Mw 7.4 rupture in NW Turkey, using waveforms recorded by a local seismic network. Applying an automatic procedure for identification and picking of fault zone head waves (FZHW) and direct P arrivals, and manually revising the picks through particle motion analysis, we identify two different groups of FZHW as well as fault zone reflected waves (FZRW). The first group of FZHW has a moveout with respect to the direct P arrivals with distance traveled along the fault, indicating a deep bimaterial interface down to the base of the seismogenic crust with an average velocity contrast of ~3.4%. The second group of FZHW has a constant time difference from the direct P arrivals and is associated with a shallow local interface bounding a low‐velocity damage zone or basin structure that extends to a depth of 4–5 km. While the first group of FZHW exists on the slower crustal block, the second group of FZHW and the FZRW are present generally on both sides of the fault. These phases add to the richness and complexity of the early P waveforms observed at stations close to a large fault. The relatively low velocity contrast across the Karadere Fault compared to values to the west may have helped stopping the Izmit rupture.

A new method to analyze the velocity spectrograms of photonic Doppler velocimetry

Ejecta mixing takes place at the interface between metal and gas under shock loading, i.e., the transport process of ejecta from metal surface happens in gas. Ejecta production and transport processes in gas are the focuses and key problems of shock wave physics at present. So far, extensive investigations have been devoted mainly to the ejecta formation from metal surface under shock-loaded conditions, and many experimental measurement techniques have been developed, such as the Asay foil, high-speed camera and holography technique. As a newly developed instrument, photon Doppler velocitymetry (PDV) which allows the simultaneous detection of velocities of multiple particles has been widely used in the dynamic impact areas, especially in micro-jetting and ejecta mixing experiments. Although PDV spectrogram includes abundant information about ejecta particles, it seems to be too hard to obtain the particle velocity history, which embarrasses the analysis and application of PDV spectrogram. In this paper, the equation of particle motion including the effects of aerodynamic damping force, pressure gradient force, and additional mass force is established, and the analytical solutions of the particle position and velocity are derived in the conditions of planar constant flow, constant flow, and constant acceleration flow. According to the analytical solutions, the characteristics of particle movement are analyzed. A simplified formulation of the relaxation time of the particle velocity, which reflects the particle decelerated speed, is given. And it is found that the relaxation time is proportional to the four-thirds power of particle diameter. Based on the characteristics of particle motion in the planar constant flow, a new method is proposed to analyze the spectrogram of PDV. The fastest velocity of particle in the mixing zone is obtained by extracting the upper part of PDV spectrogram. By integrating the fastest velocity, the time evolution of the head of mixing zone is deduced approximately. The thickness of the mixing zone can be obtained by subtracting the free surface position from the head of mixing zone. The relaxation time of particle velocity is inferred by the exponential fitting of the fastest velocity based on the motion equation of the particle in the planar constant flow. Furthermore, the equivalent diameter of the mixing zone head can also be obtained through the relaxation time. Based on the above methods, the spectrograms of various ejection mixing experiments under different shock-loaded conditions and gas environments are analyzed. The time evolutions of the mixing zone and equivalent diameter are presented, and the effects of shock loading strength and post-shock gas temperature on the mixing zone are analyzed. It is found that the deduced equivalent diameter in gas is smaller than that in vacuum, validating the pneumatic breakup of liquid metal particles in gas.

IMPROVING THE TRANSMISSION PERFORMANCE BASED ON MINIMIZING ENERGY IN MOBILE ADHOC NETWORKS

Networking is collectively no of mobile nodes allocate users to correctly detect a distant environment. These wireless mobile networks want strong but simple, scalable, energy efficient and also self organize routing algorithms. In Mobile technology small quantity of power electronics and less power radio frequency have permit the expansion of small, comparatively economical and less power nodes, are associated in a wireless mobile networkIn this study we proposed method are: energy effectiveness, energetic occurrence zone and multiple hop TRANSMIT, taking into concern between the energy of transmit nodes and distance from the transmit node to the trusted neighbor node, link weight energy utilization and distance are measured as most important constraint for decide on greatest possible path from Zone Head (ZH) to the neighbor node. In this we use the different constraints and lessen the quantity of distribution messages during the Transmit node choice point to decrease the energy utilization of the complete network.

Velocity contrast along the rupture zone of the 2010 Mw6.9 Yushu, China, earthquake from fault zone head waves

Fault zone head waves (FZHWs) travel along the bimaterial fault interface and can be used to provide high-resolution imaging of fault zone properties. Here we use aftershock data following the 2010/04/13 Mw6.9 Yushu earthquake to quantify velocity contrast along the Garzê–Yushu Fault (GYF). FZHWs are identified as low-amplitude, long-period seismic signals with polarities opposite to the direct P arrivals. We observe FZHWs at 4 stations near faults that bound both sides of the Jielong basin, which is a pull-apart basin that is partially filled by Longbao Lake. The time delays between the direct P and FZHWs increase systematically with along-strike distances, and the corresponding observed velocity contrast is on the order of 5–8%. However, we do not observe a clear increase of time delay with hypocentral depth, suggesting that the pull-apart basin forms a thick low-velocity zone that likely exists in the top few kilometers of the crust. The velocity contrast southeast of the mainshock epicenter is very small (1–3%), consistent with both field observations and seismic tomographic results.

Automatic picking of direct P, S seismic phases and fault zone head waves

Automatic picking of direct P, S seismic phases and fault zone head waves

Seismic Imaging of a Bimaterial Interface Along the Hayward Fault, CA, with Fault Zone Head Waves and Direct P Arrivals

We observe fault zone head waves (FZHW) that are generated by and propagate along a roughly 80 km section of the Hayward fault in the San Francisco Bay area. Moveout values between the arrival times of FZHW and direct P waves are used to obtain average P-wave velocity contrasts across different sections of the fault. The results are based on waveforms generated by more than 5,800 earthquakes and recorded at up to 12 stations of the Berkeley digital seismic network (BDSN) and the Northern California seismic network (NCSN). Robust identification of FZHW requires the combination of multiple techniques due to the diverse instrumentation of the BDSN and NCSN. For single-component short-period instruments, FZHW are identified by examining sets of waveforms from both sides of the fault, and finding on one (the slow) side emergent reversed-polarity arrivals before the direct P waves. For three-component broadband and strong-motion instruments, the FZHW are identified with polarization analysis that detects early arrivals from the fault direction before the regular body waves which have polarizations along the source-receiver backazimuth. The results indicate average velocity contrasts of 3–8 % along the Hayward fault, with the southwest side having faster P wave velocities in agreement with tomographic images. A systematic moveout between the FZHW and direct P waves for about a 80 km long fault section suggests a single continuous interface in the seismogenic zone over that distance. We observe some complexities near the junction with the Calaveras fault in the SE-most portion and near the city of Oakland. Regions giving rise to variable FZHW arrival times can be correlated to first order with the presence of lithological complexity such as slivers of high-velocity metamorphic serpentinized rocks and relatively distributed seismicity. The seismic velocity contrast and geological complexity have important implications for earthquake and rupture dynamics of the Hayward fault, including a statistically preferred propagation direction of earthquake ruptures to the SE.

Incorporating fault zone head wave and direct wave secondary arrival times into seismic tomography: Application at Parkfield, California

We present a three‐dimensional (3D) P wave velocity (Vp) model of the Parkfield region that utilizes existing P wave arrival time data, including fault zone head waves (FZHWs), and data from direct wave secondary arrivals (DWSAs). The first‐arrival and DWSA travel times are obtained as the global‐ and local‐minimum travel time paths, respectively. The inclusion of FZHWs and DWSAs results in as much as a 5% and a 10% increase in the across‐fault velocity contrast, respectively, for the Vp model at Parkfield relative to that of Thurber et al. [2006]. Viewed along strike, three pronounced velocity contrast regions are observed: a pair of strong positive velocity contrasts (SW fast), one NW of the 1966 Parkfield earthquake hypocenter and the other SE of the 2004 Parkfield earthquake hypocenter, and a strong negative velocity contrast (NE fast) between the two hypocenters. The negative velocity contrast partially to entirely encompasses peak coseismic slip estimated in several slip models for the 2004 earthquake, suggesting that the negative velocity contrast played a part in defining the rupture patch of the 2004 Parkfield earthquake. Following Ampuero and Ben‐Zion (2008), the pattern of velocity contrasts is consistent with the observed bilateral rupture propagation for the 2004 Parkfield earthquake. Although the velocity contrasts also suggest bilateral rupture propagation for the 1966 Parkfield earthquake, the fault is creeping to the NW here, i.e., exhibiting velocity‐strengthening behavior. Thus, it is not surprising that rupture propagated only SE during this event.

Evidence for a bimaterial interface along the Mudurnu segment of the North Anatolian Fault Zone from polarization analysis of P waves

We present results on imaging contrast of seismic velocities across the Mudurnu segment of the North Anatolian Fault Zone (NAFZ) in northwestern Turkey with polarization analysis of early P waveforms generated by near-fault seismicity and recorded by near-fault stations. The analysis uses changes in motion polarity from fault–normal to source–receiver directions to identify early-arriving fault zone head waves on the slow side of the fault, and measure the arrival times of the head and direct P waves. The moveout between the head and direct waves with increasing source–receiver distance along the fault provides an estimate of the average contrast of seismic velocities across the fault. The results indicate that the average contrast of P wave velocities across the Mudurnu segment of the NAFZ is at least 6%, with the south block being the faster side. The findings provide a basis for deriving improved event locations, focal mechanisms and estimated shaking hazard associated with earthquakes on the fault. The analysis technique can be used in other fault zones monitored with sparse seismic instrumentation.

Analytical modeling of saturated zone head response to evapotranspiration and river-stage fluctuations

Summary We investigate the response of the saturated zone (unconfined aquifer) to evapotranspiration (ET) flux at ground surface. We neglect fluid flow and storage in the unsaturated zone and treat ET as a sinusoidal forcing function at the watertable. The linearized kinematic condition is imposed at the watertable. Analytical solutions are developed for the case of flow in a domain of (a) semi-infinite extent to simulate response in a domain bounded by a river and (b) infinite lateral extent to simulate the response in a domain with no river boundaries. These solutions are fitted to observed groundwater head fluctuations recorded in observation wells at the Boise Hydrogeophysical Research Site in Idaho and the Larned Research Site in Kansas. Estimates of the amplitude of the ET flux, aquifer hydraulic conductivity, specific storage and specific yield are obtained and these compare well to published results from pumping tests conducted at the site. The field exercise is used to explore the potential for using groundwater head fluctuations to estimate ET and hydraulic parameters of unconfined aquifers.

Variations of the velocity contrast and rupture properties of M6 earthquakes along the Parkfield section of the San Andreas fault

SUMMARY We investigate the seismic velocity contrast across the San Andreas fault (SAF) in the Parkfield area using fault zone head waves (FZHW) that propagate along the bimaterial fault interface and direct P waves. We systematically analyse large data sets of near-fault waveforms recorded by several seismic networks over the period 1984–2005. Clear FZHW are observed at many stations on the NE side of the fault in the creeping section of the SAF north of Middle Mountain (MM). This indicates the presence of a sharp bimaterial interface and that the NE side of the fault has lower seismic velocities in that region. The obtained P-wave velocity contrast is about 5–10 per cent north of MM, and it systematically decreases to 0–2 per cent near Gold Hill (GH). The along-strike variations of the velocity contrast are consistent with geological observations of a sliver of high-velocity rock immediately to the NE of the SAF near GH, associated with the GH fault, and existing 3-D seismic tomography results. The obtained imaging results offer an explanation for the mixed rupture directions of the M6-type Parkfield earthquakes. The strong velocity contrast around MM is expected to produce a preferred propagation direction to the SE for earthquakes that nucleate near MM (e.g. the 1934 and 1966 Parkfield earthquakes). In contrast, the near-zero velocity contrast and multiple fault branches near GH imply that earthquakes that nucleate near GH (e.g. the 2004 Parkfield earthquake) are not expected to have a preferred propagation direction to the SE, and are likely to propagate in directions that are controlled by other factors such as structural and stress heterogeneities. The observed systematic reduction of the velocity contrast along the SAF from NW of MM to SE of GH provides a dynamic arrest mechanism for earthquakes that nucleate in the northern part of the Parkfield section and propagate to the SE, and a dynamic arrest mechanism for earthquakes that nucleate in the southern section and propagate to the NW.

Velocity contrast along the Calaveras fault from analysis of fault zone head waves generated by repeating earthquakes

We systematically investigate the velocity contrast along the Calaveras fault that ruptured during the 1984 Morgan Hill earthquake using fault zone head waves (FZHW) that refract along the fault interface. We stack waveforms in 353 sets of repeating clusters, and align the peaks or troughs of the direct P waves assuming right‐lateral strike‐slip focal mechanisms. The obtained velocity contrasts are 2–3% and 12–14% NW and SE of station CCO, respectively. The FZHW and the fault plane outlined by the relocated seismicity SE of CCO are more complicated than those NW of CCO. The results can be explained by a relatively simple and sharp fault interface in the NW, and a complicated fault structure with a presence of a low‐velocity zone in the SE. The along‐strike variations in the strength of the velocity contrast are consistent with surface geological mapping and recent 3D tomography studies in this region.

Imaging the deep structure of the San Andreas Fault south of Hollister with joint analysis of fault zone head and directParrivals

SUMMARY We perform a joint inversion of arrival time data generated by direct P and fault zone (FZ) head waves in the San Andreas Fault south of Hollister, CA, to obtain a high-resolution local velocity structure. The incorporation of head waves allows us to obtain a sharp image of the overall velocity contrast across the fault as a function of depth, while the use of near-fault data allows us to resolve internal variations in the FZ structure. The data consist of over 9800 direct P and over 2700 head wave arrival times from 450 events at up to 54 stations of a dense temporary seismic array and the permanent northern California seismic network in the area. One set of inversions is performed upon the whole data set, and five inversion sets are performed on various data subsets in an effort to resolve details of the FZ structure. The results imply a strong contrast of P-wave velocities across the fault of ∼50 per cent in the shallow section, and lower contrasts of 10‐20 per cent below 3 km, with the southwest being the side with faster velocities. The presence of a shallow low velocity zone around the fault, which could corresponds to the damage structures imaged in trapped wave studies, is detected by inversions using subsets of the data made up of only stations close to the fault. The faster southwest side of the fault shows the development of a shallow low velocity FZ layer in inversions using instruments closer and closer to the fault (<5 and <2 km). Such a feature is not present in results of inversions using only stations at greater distances from the fault. On the slower northeast side of the fault, the presence of a low velocity shallow layer is only detected in the inversions using the stations within 2 km of the fault. We interpret this asymmetry across the fault as a possible indication of a preferred propagation direction of earthquake ruptures in the region. Using events from different portions of the fault, the head wave inversions also resolve small-scale features of the fault visible in the surface geology and relocated seismicity.

Discontinuity of the Mozumi–Sukenobu fault low-velocity zone, central Japan, inferred from 3-D finite-difference simulation of fault zone waves excited by explosive sources

We delineate shallow structures of the Mozumi–Sukenobu fault, central Japan, using fault zone waves generated by near-surface explosions and detected by a seismometer array. Two explosive sources, S1 and S2, were placed at a distance of about 2 km from the array, and the other two, S3 and S4, were at a distance of about 4 km. Fault zone head waves and fault zone trapped waves following direct P wave arrivals were clearly identified in the seismograms recorded by a linear seismometer array deployed across the fault in a research tunnel at a depth of 300 m. Synthetic waveforms generated by a 3-D finite-difference (3-D FD) method were compared with observed fault zone waves up to 25 Hz. The best fitting model indicates a 200-m-wide low-velocity zone extending at least to shot site S1 located 2 km east of the seismic array with a 20% decrease in the P wave velocity relative to the wall rock. The width of the low-velocity zone is consistent with the fault zone defined by direct geological observation in the research tunnel. However, the low-velocity zone should disappear just to the east of the site S1 to explain the observed fault zone waves for shot S3 and S4 located 4 km east of the seismometer array. Yet the observation and the simulation show notable trapped wave excitation even though shots S3 and S4 are outside the fault zone. These results indicate that (1) the effective waveguide for seismic waves along the fault does not exist east of source site S1 although the surface traces of the fault are observed in this region, and (2) considerable trapped waves can be excited by sources well outside the fault zone. These results highlight the along-strike variability in fault zone structure.

3-D finite-difference simulation of seismic fault zone waves—Application to the fault zone structure of the Mozumi-Sukenobu fault, central Japan—

Fault zone waves have the potential to be a powerful tool to reveal the fine structure of a fault zone down to the seismogenic depth. Seismic fault zone waves include head waves, trapped waves and direct body waves propagating in the fault zone. 3-D numerical simulation is necessary to interpret the waveforms in the presence of low-velocity zones with relatively complex fault structure. We computed finite difference (FD) synthetic seismograms to fit the seismograms of explosions, which contain frequencies up to 25 Hz, recorded by a linear seismometer array across the Mozumi-Sukenobu fault, central Japan. We find fault zone head waves, direct P waves propagating within the low-velocity zone and wave trains following the direct P waves associated with the fault for both observed and synthetic waveforms. Thus, modelling of fault zone waves is expected to determine details of complex fault zone structure.

The dislocation structure of crack tip plastic zones in a cobalt base superalloy

An investigation has been made of the dislocation structure of the plastic zone head of crack tips in a Co-base superalloy during in situ tensile deformation. The results show that the dislocation distribution in the plastic zone depends on both the orientation of the tensile axis and the stress state at the crack tip.

Three-trophic-level interactions in cattail hybrid zones.

Plant-herbivore and herbivore-parasitoid wasp interactions were examined in three hybrid zones of the cattails Typha latifolia and T. angustifolia in south-eastern Michigan over a 2-year period. Patterns of resource use by two lepidopteran species of seed-eating herbivores were studied and herbivore densities sustained by the hybrid cattail T. x glauca and its parental species were determined. Densities of the commoner seed-eating lepidopteran, Lymnaecia phragmitella, were found to be highest in seed heads of both parental species and lowest in hybrid seed heads in zones of hybridization, thus supporting the hybrid resistance hypothesis of Fritz et al. (1994). Densities of the second herbivore, Dicymolomia julianalis, on the hybrid were lower than on the parental T. latifolia, but did not differ from the mean of the combined herbivore densities of the two parental species. D. julianalis in cattails appears to fit the additive hypothesis (Fritz et al. 1994). Parasitism of L. phragmitella by four species of parasitoid wasp, Itoplectis conquisitor (Ichneumonidae), Scambus hispae (Ichneumonidae), Macrocentrus delicatus (Braconidae), and Temelucha gracilipes (Ichneumonidae), was studied to determine if rates of parasitization by these natural enemics on the different cattails were similar to the patterns of plant exploitation exhibited by their hosts. Parasitism rates of L. phragmitella were significantly higher in larvae reared on hybrid cattails. This study reveals two different patterns of hybrid utilization by two very similar herbivores. Opposite patterns of plant utilization were found for the parasitoids compared with their host (L. phragmitella) in cattail hybrid zones.

Joint inversion of fault zone head waves and direct P arrivals for crustal structure near major faults

A newly recognized class of seismic phases, namely fault zone head waves arising from refraction at a transfault velocity contrast, provides additional constraints to direct P waves in inversions of near‐fault arrival time data for earthquake location and velocity structure. Incorporation of fault zone head waves in the inversion process increases the available data and broadens the spatial coverage of ray paths between sources and receivers. Equally important, the explicit recognition of fault zone head waves eliminates a source of error resulting from misidentifying head wave first arrivals as direct P waves. A simple algorithm for the joint inversion of fault zone head waves and direct P phases is illustrated with observed and synthetic data. Application to a small data set recorded by the borehole seismic network at Parkfield, California, provides separate seismic velocity depth profiles for the crustal blocks on the two sides of the San Andreas fault. For depths less than 3 km the obtained velocity contrast is 10–20%. For greater depths it decreases to 3–7%. Numerical tests with synthetic data show that for sources with known locations and for well located local earthquakes (randomized mislocation errors of up to 600 m) proper use of fault zone head waves can significantly improve the accuracy of the fitted velocity structure. The results of this work motivate the inclusion of fault zone head waves in state‐of‐the‐art joint structure‐hypocenter inversions using high quality near‐fault data.