bluuebunny/crossref_metadata_2025_split huggingface dataset:
The earthquake hazard alert of September 1982 in Southern Tobago
Authors: Morgan F. D. , Wadge G. , Latchman J. , Aspinall W. P. , Hudson D. , Samstag F. 
Published: July 2021

AbstractAn earthquake swarm that occurred in the vicinity of the island of Tobago (West Indies) during the latter half of 1982 was monitored in the near-field by a five-station seismograph network. The monitoring of the swarm eventually led to the issuing of a potential earthquake hazard alert, 3 days prior to the major energy release (earthquake magnitude mb = 5.2). We discuss the reasons for issuing this alert. In particular, daily monitoring of the changing b value and energy release was used to constrain estimates of future earthquake behavior. The aftershock seismicity showed activity in a direction trending west to WNW. This is in good agreement with the focal mechanism of the main earthquake which showed right-lateral strike-slip motion along an E-W fault plane dipping steeply (71°) to the north. This active fault appears to form part of the previously unrecognized Southern Tobago Fault System for which there is evidence in the geology of the Late Neogene rocks of the island.
Seismic wave energy inferred from long-period body wave inversion
Authors: Kikuchi Masayuki , Fukao Yoshio 
Published: July 2021

AbstractThe seismic wave energy is evaluated for 35 large earthquakes by inverting far-field long-period P waves into the multiple-shock sequence. The results show that the seismic wave energy thus obtained is systematically less than that inferred from the Gutenberg-Richter's formula with the seismic magnitude. The difference amounts to one order of magnitude. The results also show that the energy-moment ratio is well confined to a narrow range: 10−6 &lt; ES/Mo &lt; 10−5 with the average of ∼5 × 10−6. This average value is exactly one order of magnitude as small as the energy-moment ratio inferred from the Gutenberg-Richter's formula using the moment magnitude. Comparing the energy-moment ratio with Δσo/2μ, where Δσo and μ are the stress drop and the rigidity, we obtain an empirical relation: ES/Mo ∼ 0.1 × Δσ0/2μ. Such a relation can be interpreted in terms of a subsonic rupture where the energy loss due to cohesion is not negligible to the seismic wave energy.
Attenuation of modified Mercalli intensity with distance in Mexico
Authors: Chávez Mario , Castro Raul 
Published: July 2021

AbstractTwo relations are proposed to predict the attenuation of Modified Mercalli Intensity (I) with distance (D) for Mexican earthquakes, i.e.ln I = B 0 + B 1 ln ( D / D ' ) + B 2 ( D − D ' ) + B 3 ln M s ln I = B 0 + B 1 ( D / D ' ) + B 2 ln ( D − D ' ) + B 3 ln M sMs is the earthquake surface-wave magnitude, D′ is a distance related to the maximum I mapped for an earthquake, I′ or to Ms. The coefficients Bi, i = 0, 1, 2, 3 were obtained by fitting in a least-square sense the information contained in the intensity maps of 32 events to the relations. Those events were classified in three groups according to their epicentral location, focal mechanism, and depth, i.e., events related to the subduction-zone intermediate-depth earthquakes in south-central Mexico and to shallow crustal events along the Trans-Mexican Volcanic Belt.The I predicted by the proposed relations compare well with the I observed for historical earthquakes not included in the fitting. Results obtained from a parametrical study showed that the attenuation of I with D is different for each of the three types of earthquakes. For distances of less than about 200 km, the earthquakes associated with the subduction zone have a larger attenuation than the ones originating in the south-central region of Mexico; for greater distances (D &gt; 200 km), the opposite behavior is observed. The events located in the Trans-Mexican Volcanic Belt have a larger attenuation with distance than that of events in the other two regions. From these results, it seems advisable in Mexico to use several attenuation relations to estimate the seismic hazard at a site, depending on the particular tectonic setting and the path of the events under consideration.
A procedure for calibrating short-period telemetered seismograph systems
Authors: Chapman M. C. , Snoke J. A. , Bollinger G. A. 
Published: July 2021

AbstractEfficient low-frequency calibration of the entire seismograph system can be accomplished by Fourier analysis of the system response to automatically generated transient test functions applied to the seismometer calibration coil. Typically, such calibrations are restricted to frequencies less than 10 Hz by the ambient ground motion, system noise, and limited dynamic range. To extend the calibration to a broader frequency range, we disconnect the seismometer and take advantage of the fact that the relative amplitude response of the electronic components in most systems can be measured with high accuracy at frequencies from as low as 0.02 Hz to the Nyquist frequency (e.g., 50 Hz) using standard electronics test equipment. The low-frequency amplitude response of the seismometer can then be isolated by dividing the total system response by that obtained for the electronic components. An iterative least-squares procedure is used to estimate the natural frequency and damping coefficient of the seismometer, along with a scaling parameter that specifies the absolute gain of the system. The phase response of the system is calculated directly from the amplitude response using the Hilbert transform. The procedure assumes that the seismometer is an ideal damped harmonic oscillator and that the system as a whole acts as a minimum phase filter. The only instrumental constants that must be known from independent measurement are the seismometer calibration coil force constant and the inertial mass.
Network-averaged teleseismicP-wave spectra for underground explosions. Part I. Definitions and examples
Authors: Murphy J. R. , Barker B. W. , O'Donnell A. 
Published: July 2021

AbstractA new procedure is described for estimating network-averaged P-wave spectra from short-period, teleseismic recordings of explosions. This procedure is then applied to a large sample of approximately 1000 digitized Nevada Test Site (NTS) explosion seismograms to simultaneously derive estimates of frequency-dependent station correction factors and network-averaged P-wave spectra for each of the 50 selected explosions. An analysis of the station correction factors is then presented which demonstrates that the Veith-Clawson (1972) B(Δ) curve for time domain mb adequately describes the teleseismic distance dependence of the spectral amplitude data over the entire short-period band extending from 0.50 to 2.25 Hz. A simplified scaling analysis of the network-averaged spectra is described and used to confirm the fact that the P-wave source coupling characteristics below the water table at the Yucca Flat and Pahute Mesa testing areas of NTS are essentially identical. We conclude that this new spectral measure can provide robust means for comparing different explosion testing areas.
A satellite-based digital data system for low-frequency geophysical data
Authors: Silverman Stan , Mortensen Carl , Johnston Malcolm 
Published: July 2021

Abstract
A reliable method for collection, display, and analysis of low-frequency geophysical data from isolated sites, which can be throughout North and South America and the Pacific Rim, has been developed for use with the Geostationary Operational Environmental Satellite (GOES) system. Geophysical data primarily intended for earthquake hazard and crustal deformation monitoring are digitized with either 12-bit or 16-bit resolution and transmitted every 10 min through a satellite link to a bank of UNIX-based computers in Menlo Park, California. There the data are available for analysis and display within a few seconds of their transmit time. This system provides real-time monitoring of crustal deformation parameters such as tilt, strain, fault displacement, local magnetic field, crustal geochemistry, and water levels, as well as meteorological and other parameters, along faults in California and Alaska, and in volcanic regions in the western United States, Rabaul, and other locations in the New Britain region of the South Pacific. Various mathematical, statistical, and graphical algorithms process the incoming data to detect changes in crustal deformation and fault slip that may indicate the first stages of catastrophic fault failure. Alert trigger levels based on physical models, signal resolution, and previous history have been defined for particular instrument types. Computer-driven remote paging and mail systems are used to notify appropriate personnel when alarm status is reached. The system supports continuous historical records of low-frequency geophysical data, software for extensive analysis of these data, and programs for modeling fault rupture with and without seismic radiation, as well as providing an environment for real-time attempts at earthquake prediction.
An exact anelastic model for the free-surface relfection ofPandS-I waves
Authors: Borcherdt R. D. , Glassmoyer G. 
Published: July 2021

AbstractExact anelastic solutions incorporating inhomogeneous waves are used to model numerically S-I and P waves incident on the free surface of a low-loss anelastic half-space. Anelastic free-surface reflection coefficients are computed for the volumetric strain and displacement components of inhomogeneous wave fields. For the problem of an incident homogeneous S-I wave in Pierre shale, the largest strain and displacement amplitudes for the reflected P wave occur at angles of incidence for which the particle motion for the reflected inhomogeneous P wave is elliptical (minor/major axis = 0.6), the specific absorption (QP−1) is greater (300 per cent) and the velocity is less (25 per cent) than those for a corresponding homogeneous P wave, the direction of phase propagation is not parallel to the free surface, and the amplitude of the wave shows a significant increase with depth (6 per cent in one wavelength). Energy reflection coefficients computed for this low-loss anelastic model show that energy flow due to interaction of the incident and reflected waves reach maxima (30 per cent of the incident energy) near large but nongrazing angles of incidence. For the problem of an incident homogeneous P wave in Pierre shale, the inhomogeneity of the reflected S wave is shown not to contribute to significant variations in wave field characteristics over those that would be expected for a homogeneous wave.
High-frequencyP-wave attenuation determination using multiple-window spectral analysis method
Authors: Zhu Tianfei , Chun Kin-Yip , West Gordon F. 
Published: July 2021

AbstractYellowknife array (Northwest Territories, Canada) recordings of nuclear explosions detonated at French Tuamotu, South Pacific and Shagan River, Eastern Kazakhstan (USSR) test sites are used to derive t* values via the application of the spectral decay method. An important factor that limits the reliability of this widely used method is the degree of accuracy with which one is able to determine the signal spectral shape. For transient, pulse-like, short-period teleseismic phases, the conventional single-window spectral estimate methods may not be appropriate due to the trade-off betgween the leakage resistance and variance. A recently developed, multiple-window spectral analysis method is used in this study to effectively control spectral leakage, a capability that is especially important when analyzing seismic data characterized by a rapid high-frequency fall-off rate, such as the French Tuamotu explosion data. We compare the t* estimates obtained using a conventional single-window method with those obtained using the multiple-window method and show that the latter are more reliable. The t* (0.5 to 4.5 Hz) found by the multiple-window method for the Tuamotu-Yellowknife path is 0.66 sec. For the Eastern Kazakhstan-Yellowknife path, the multiple-window t* estimate is 0.42 sec in the 0.5 to 4.5 Hz range; a smaller value is obtained at higher frequencies (4.5 to 8 Hz).
A comparison of finite-difference and fourier method calculations of synthetic seismograms
Authors: Daudt C. R. , Braile L. W. , Nowack R. L. , Chiang C. S. 
Published: July 2021

Abstract
The Fourier method, the second-order finite-difference method, and a fourth-order implicit finite-difference method have been tested using analytical phase and group velocity calculations, homogeneous velocity model calculations for disperson analysis, two-dimensional layered-interface calculations, comparisons with the Cagniard-de Hoop method, and calculations for a laterally heterogeneous model. Group velocity rather than phase velocity dispersion calculations are shown to be a more useful aid in predicting the frequency-dependent travel-time errors resulting from grid dispersion, and in establishing criteria for estimating equivalent accuracy between discrete grid methods. Comparison of the Fourier method with the Cagniard-de Hoop method showed that the Fourier method produced accurate seismic traces for a planar interface model even when a relatively coarse grid calculation was used. Computations using an IBM 3083 showed that Fourier method calculations using fourth-order time derivatives can be performed using as little as one-fourth the CPU time of an equivalent second-order finite-difference calculation. The Fourier method required a factor of 20 less computer storage than the equivalent second-order finite-difference calculation. The fourth-order finite-difference method required two-thirds the CPU time and a factor of 4 less computer storage than the second-order calculation. For comparison purposes, equivalent runs were determined by allowing a group velocity error tolerance of 2.5 per cent numerical dispersion for the maximum seismic frequency in each calculation. The Fourier method was also applied to a laterally heterogeneous model consisting of random velocity variations in the lower half-space. Seismograms for the random velocity model resulted in anticipated variations in amplitude with distance, particularly for refracted phases.
Inversion of near-sourceSpolarization for parameters of double-couple point sources
Authors: Bernard Pascal , Zollo Aldo 
Published: July 2021

AbstractWe propose an inversion method for retrieving the focal parameters of small to moderate earthquakes by using the near-source S-wave polarizations, which are expected to be less sensitive than amplitude data to source details or propagation effects. We first studied the variability of the polarization vector for complete synthetic records generated in simple media with a shallow low-velocity layer, for various distances (0 to 50 km), source depths (1 to 15 km), and mechanisms. In the frequency band 1 to 2 Hz, a polarization fluctuation of less than 20° is found for sources deeper than 5 km. The mean angular difference between ray theory and complete field polarization is less than 10° when the complete waveform meets the two following criteria: (1) The polarization is nearly stable (less than 30° of variability) and (2) the motion is nearly horizontal (vector dip less than 30°).The inversion method uses a norm related to the angular difference in polarization between the real and synthetic waveforms generated by a point double couple. As the problem is highly nonlinear, the model space (strike, dip, slip, location) should be finely sampled and systematically explored in the whole domain of interest. We tested the inversion resolution with synthetic data for a strike-slip and a dip-slip source at 10 km in depth (no error in location) recorded at eight stations within 30 km, assuming an error of 25° on the synthetic polarization. The dip-slip inversion gives a good resolution in dip (15° of uncertainty), but a strong correlation between strike and slip, because no recording site was close to the near vertical principal axis of the stress tensor in the test. On the contrary, the near horizontal major axis of the tensor is very well constrained. The strike-slip inversion gives a good resolution in the three parameters, with uncertainties of about 10°. A 25° change in the strike, dip, or slip angle statistically results in a 25° rotation of the polarization. With numerous stations, the overdetermination of the problem reduces the model error to values lower than 25°. The absence of records in specific areas introduces additional solutions for the possible mechanisms. Finally, the sensitivity of polarization to 3 km shift in source location is globally smaller than for 25° of rotation of any fault angle. The application of this method to real data requires the evaluation of the reliability in the polarizations computed for simplified media. An uncertainty of 25° is expected to be a reasonable assumption for distances smaller than 30 km in the 1 to 2 Hz frequency band; more generally, the error is expected to increase with distance and frequency.
On the relocation of earthquake clusters. A case history: The Arkansas earthquake swarm
Authors: Pujol José , Chiu Jer-Ming , Johnston Arch , Chin Byau-Heng 
Published: July 2021

AbstractA portable digital network (the PANDA array) of 40 three-component stations with an aperture of about 35 km was deployed for 4 months in the Arkansas swarm area in 1987. Only 12 swarm events occurred during the deployment, in contrast to the intense seismic activity that characterized this region in 1982 to 1984. These events were relocated using a joint hypocentral determination technique (JHD). The JHD method used here allows for the simultaneous determination of P- and S-wave station corrections while providing information on the uniqueness of the solution based on the singular values of a matrix related to the station corrections. P-wave station corrections, determined when all nonzero singular values were used in the computations (or with the two smallest nonzero singular values deleted), show a circular pattern of positive values surrounded by negative values. The epicentral area is localized slightly displaced from the center of the pattern. Since positive and negative corrections correspond to velocities that are lower and higher, respectively, than the average, our results indicate that the swarm area is characterized by seismic velocities lower than those of its surroundings. Independent information on this region is afforded by reflection seismic lines recorded in the swarm area and its vicinity, which show that the hypocenters are located in a region where strong reflectors completely lose their coherence, indicating that this volume is anomalous when compared to surrounding crust. Additional support for a low-velocity zone comes from the results of a 3-D velocity inversion of the same PANDA data. A selected subset of data recorded digitally by the USGS in 1982 was also relocated. Comparison with the results from the PANDA data shows that the seismic activity did not migrate over a 5-yr period and that it is concentrated within a small volume between about 3 km and 6 km depth. While the results of this study do not determine the ultimate cause of the Arkansas swarm, the discovery of a pronounced localized low velocity zone is consistent with a previously proposed magmatic intrusion or a zone of highly fractured, fluid-filled crust.
Pelatihan Pembuatan Trichokompos untuk Mengendalikan Penyakit Tanaman di Desa Banua Supanggal
Authors: Mariana Mariana , Budi Ismed Setya , Marsuni Yusriadi , Pramudi Muhammad Indar , Salamiah Salamiah , Fachruzi Ismed 
Published: July 2021

Upaya pengendalian penyakit tanaman sampai saat ini oleh petani di desa Banua Supanggal Kecamatan Pandawa masih bertumpu pada penggunaan pestisida sintetik. Akibatnya jumlah konsumsi penggunaan pestisida terus meningkat. Alternatif pengendalian yang aman dan ramah lingkungan adalah penggunaan agensia hayati spesifik lokasi. Sudah banyak hasil penelitian yang membuktikan bahwa penggunaan Trichokompos efektif untuk pengendalian penyakit tanaman pertanian, dan perlu disosialisasikan ke petani di desa. Pengendalian hayati menggunakan Trichokompos hasil dari campuran jamur antagonis Trichoderma sp spesifik lokasi dengan kotoran ternak sebagai media formulasi perbanyakan masih belum dikenal petani di desa Banua Supanggal. Kegiatan ini diawali pertemuan diskusi dengan ketua kelompok tani untuk melihat permasalahan di pertanaman petani dan dilanjutkan pengamatan penyakit utama yang ada. Tahap kedua penyuluhan kepada anggota kelompok tani dan dilanjutkan dengan praktek pembuatan Trichokompos. Hasil kegiatan ini menunjukkan petani sangat antusias mengikuti semua kegiatan mulai pembuatan sampai aplikasi di lahan. Pada kegiatan pendampingan lanjutan sudah menunjukkan petani mempraktekkan cara pembuatan di kelompok masing-masing. Hasil monitoring dan evaluasi sudah membuktikan bahwa Trichokompos sudah berhasil diproduksi oleh petani secara mandiri.
The impact of prep class education on effective English requestive e-mails written by students in Turkey
Authors: Bacak Begum 
Published: July 2021

For the past years, cross-cultural and interlanguage pragmatics have focused on native and non-native speech act descriptions, and only a small number of studies have investigated the preparatory class effect involved in speech act productions. To bridge the gap, this study aims to investigate the degree of directness and amount of lexical / phrasal internal and external modifications of requestive e-mails employed by 25 first grade students of English Language and Literature department with preparatory education and 25 first grade students of English Language and Literature department without preparatory education in their in a state university. It also aims to explore whether there is a difference between two groups according to the degree of imposition while making requests. The participants were given discourse completion tests in e-mail format including two different situations with low and high imposition levels and asked to write two requestive e-mails to their non-native professor. The e-mails were analyzed and classified based on Economidou-Kogetsidis’s (2011) framework which relies on Blum- Kulka et al. (1989) and Biesenbach-Lucas (2006, 2007). Based on the percentages and frequencies, the students with preparatory class education were compared to the students without preparatory class education, with respect to their usage of request strategies, lexical/phrasal internal modification and external modification. The results indicated that these two groups had both similarities and differences with respect to the degree of directness, the amount of internal and external modifications. Turkish ELL learners with and without prep class education employed more direct strategies in both situations. However, the group without prep class education employed more conventionally indirect strategies than the group with prep class education. None of the participants used non-conventionally indirect strategies. The group with prep class education used more internal modification than the group without prep class education. The most common internal modification was the consultative device in both groups. As for external modification, the group with prep class education utilized more supportive moves than the group without prep class education. Grounder was the most preferred supportive move by both groups.

Keywords: Turkish ELL learners; requestive e-mails; academic e-mails; directness.