72 research outputs found
Multiple CMT source analysis of the 2004 Sumatra earthquake
While it is agreed that the great Sumatra earthquake of
December 26, 2004 was among the largest earthquakes of
the past century, there has been disagreement on how large
it was, which part of the fault ruptured, and how the rupture
took place. We present a centroid-moment-tensor (CMT)
analysis of the earthquake in which multiple point sources
are used in the inversion to mimic a propagating slip pulse.
The final model consists of five point sources, with the
southernmost sources accounting for the majority of the
moment release. The presumed fault planes of the southern
sources strike northwest, while those in the north strike
northeast, consistent with the geometry of the subduction
trench. Slip on the fault is found to be more oblique in the
north than in the south. The inversion with five sources
leads to a moment magnitude for the Sumatra earthquake of
M_W = 9.3, consistent with estimates from long-period
normal-mode amplitudes
Seismic radiation by magma injection: An anomalous seismic event near Tori Shima, Japan
The earthquake with a bodywave magnitude m_b=5.5, which occurred near Tori Shima, Japan, on June 13, 1984 (origin time: 0229:25.3 UT, 31.448°N, 140.036°E, depth of 10 km, m_b =5.5, M_S=5.5) is anomalous because it generated tsunamis which are disproportionately large for the magnitude of the earthquake. At Hachijo Island, 150 km from the epicenter, tsunamis were visually observed with peak-to-peak amplitude of 130 to 150 cm. Long-period seismic radiation is also anomalous. Love waves are almost absent, and Rayleigh waves are radiated with equal amplitude and phase in all directions. A simple double-couple model cannot explain these observations. With the assumption of no net volume change at the source, these data can be best explained with a compensated linear vector dipole (CLVD) with the principal tensional dipole in the vertical direction. The scalar moment of this dipole is 4×10^(24) dyn cm. Moment tensor inversions of long-period body waves and surface waves yield an almost identical solution. This CLVD source can be interpreted as horizontal fluid injection. The location of the event is in the Smith depression which is one of the nascent back arc basins just behind the Bonin arc. These basins are filled with thick sediments, and numerous young volcanoes are found near this site. Magmatic injection is most likely to occur in this tectonic environment. However, the time scale of the seismic event seems too short for magma injection to occur. A more likely mechanism involves water-magma interaction. The injection may be viewed as hydrofracturing driven by supercritical water heated by injected magma. The estimated volume of injected water is about 0.018 km^3 and that of basaltic magma is about 10% of this. This type of deformation is more efficient for tsunami generation than faulting with the same scalar moment
Исследование влияния состава материала на основе эпоксиполиэфирной смолы на его свойства
Материалы XX Междунар. науч.-техн. конф. студентов, аспирантов и молодых ученых, Гомель, 23–24 апр. 2020 г
Production of eta and 3pi mesons in the pd->3HeX reaction at 1360 and 1450 MeV
The cross sections of the pd -> 3He eta, pd -> 3He pi0 pi0 pi0 and pd -> 3He
pi+ pi- pi0 reactions have been measured at beam kinetic energies T_p= 1360 MeV
and T_p= 1450 MeV using the CELSIUS/WASA detector setup. At both energies, the
differential cross section dsigma/dOmega of the eta meson in the pd -> 3He eta
reaction shows a strong forward-backward asymmetry in the CMS. The ratio
between the pd -> 3He pi+ pi- pi0 and the pd -> 3He pi0 pi0 pi0 cross sections
has been analysed in terms of isospin amplitudes. The reconstructed invariant
mass distributions of the pi-pi, 3He-pi and 3He-2pi systems provide hints on
the role of nucleon resonances in the 3pi production process.Comment: Shorter version accepted to EPJA 10 pages 14 figure
The pp -> pp pi pi pi reaction channels in the threshold region
The cross section for prompt neutral and charged three pion production in pp
interactions was measured at excess energies in the range 160 - 217 MeV. That
comprises the first measurement of the pp->pp pi0pi0pi0 reaction and the
comparison with the pp->pp pi+pi-pi0 reaction, in a very direct way. The
experiment was performed above the eta meson production threshold and the cross
section normalization was obtained from a concurrent measurement of the
reaction pp->pp eta with the eta decaying into 3 pions. Since the same final
states are selected, the measurement has a low systematical error. The measured
cross section ratio sigma(pp->pp pi+pi-pi0)/sigma(pp->pp pi0\pi0\pi0) is
compared to predictions of dominance of different isobars in the intermediate
state.Comment: 12 pages, 4 figures New discussion on the pp->pp3pi reaction
mechanis
Close-to-threshold Meson Production in Hadronic Interactions
Studies of meson production at threshold in the hadron--hadron interaction
began in the fifties when sufficient energies of accelerated protons were
available. A strong interdependence between developments in accelerator
physics, detector performance and theoretical understanding led to a unique
vivid field of physics. Early experiments performed with bubble chambers
revealed already typical ingredients of threshold studies, which were
superseded by more complete meson production investigations at the nucleon beam
facilities TRIUMF, LAMPF, PSI, LEAR and SATURNE. Currently, with the advent of
the new cooler rings as IUCF, CELSIUS and COSY the field is entering a new
domain of precision and the next step of further progress.
The analysis of this new data in the short range limit permits a more
fundamental consideration and a quantitative comparison of the production
processes for different mesons in the few--body final states. The
interpretation of the data take advantage of the fact that production reactions
close-to-threshold are characterized by only a few degrees of freedom between a
well defined combination of initial and exit channels. Deviations from
predictions of phase-space controlled one-meson-exchange models are indications
of new and exciting physics. Precision data on differential cross sections,
isospin and spin observables -- partly but by no means adequately available --
are presently turning up on the horizon. There is work for the next years and
excitement of the physics expected. Here we try to give a brief and at the same
time comprehensive overview of this field of hadronic threshold production
studies.Comment: 100 pages, Review article to be published in Prog. Part. Nucl. Phys.
Vol. 49, issue 1 (2002
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stability. Pollinators face numerous threats, including changes in land-use and management intensity, climate change,
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well-documented declines in some wild and managed pollinators in several regions of the world. However, many effective
policy and management responses can be implemented to safeguard pollinators and sustain pollination services
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