124 research outputs found
Space-Time Diffusion of Ground and Its Fractal Nature
We present evidences of the diffusive motion of the ground and tunnels and
show that if systematic movements are excluded then the remaining uncorrelated
component of the motion obeys a characteristic fractal law with the
displacement variance dY^2 scaling with time- and spatial intervals T and L as
dY^2 \propto T^(Alpha)L^(Gamma) with both exponents close to 1. We briefly
describe experimental methods of the mesa- and microscopic ground motion
detection used in the measurements at the physics research facilities sensitive
to the motion, particularly, large high energy elementary particle
accelerators. A simple mathematical model of the fractal motion demonstrating
the observed scaling law is also presented and discussed.Comment: 83 pages, 46 fig
Earthquake source parameters and scaling relationships in Hungary (central Pannonian basin)
Abstract Fifty earthquakes that occurred in Hungary (central
part of the Pannonian basin) with local magnitude ML
ranging from 0.8 to 4.5 have been analyzed. The digital
seismograms used in this study were recorded by six permanent
broad-band stations and twenty short-period ones at
hypocentral distances between 10 and 327 km. The displacement
spectra for P- and SH-waves were analyzed according
to Brune’s source model. Observed spectra were corrected
for path-dependent attenuation effects using an independent
regional estimate of the quality factor QS. To correct spectra
for near-surface attenuation, the k parameterwas calculated,
obtaining it fromwaveforms recorded at short epicentral distances.
The values of the k parameter vary between 0.01 to
0.06 s with a mean of 0.03 s for P-waves and between 0.01
to 0.09 s with a mean of 0.04 s for SH-waves. After correction
for attenuation effects, spectral parameters (corner
frequency and low-frequency spectral level) were estimated
by a grid search algorithm. The obtained seismic moments
range from4.21×1011 to 3.41×1015 Nm (1.7≤Mw ≤4.3).
The source radii are between 125 and 1343 m. Stress drop
values vary between 0.14 and 32.4 bars with a logarithmic
mean of 2.59 bars (1 bar = 105 Pa). From the results, a linear
relationship between local andmomentmagnitudes has been
established. The obtained scaling relations show slight evidence
of self-similarity violation. However, due to the high
scatter of our data, the existence of self-similarity cannot be
excluded
Intraplate seismicity and releated mantle hydration at the Nicaraguan trench outer rise
We examine micro-earthquake records from a dense temporary array of ocean bottom seismometers (OBS) and hydrophones that has been installed from September to November 2005 at the trench outer rise offshore Nicaragua. Approximately 1.5 locatable earthquakes per day within the array of 110 × 120 km show the high seismic activity in this region. Seismicity is restricted to the upper ∼15 km of the mantle and hence where temperatures reach 350–400 °C, which is smaller than values observed for large mantle intraplate events (650 °C). Determination of moment tensor solutions suggest a change of the stress region from tensional in the upper layers of the oceanic plate to compressional beneath. The neutral plane between both regimes is located at ∼6–9 km beneath Moho and thus very shallow. Fluids, which are thought to travel through the tensional fault system into the upper mantle, may not be able to penetrate any deeper.
The earthquake catalogue, which seems to be complete for magnitudes above Mw = 1.6–1.8, suggests a strong change of the lithospheric rheology when approaching the trench. And b-factors, that is the ratio between small and large earthquakes increase significantly in the closest 20 km to the trench axis, implying that the crust and upper mantle is massively weakened and hence ruptures more frequently but under less release of stress. We explain this with a partly serpentinized upper mantle
Unearthing the Infrastructure: Humans and Sensors in Field-Based Scientific Research
Distributed sensing systems for studying scientific phenomena are critical applications of information technologies. By embedding computational intelligence in the environment of study, sensing systems allow researchers to study phenomena at spatial and temporal scales that were previously impossible to achieve. We present an ethnographic study of field research practices among researchers in the Center for Embedded Networked Sensing (CENS), a National Science Foundation Science & Technology Center devoted to developing wireless sensing systems for scientific and social applications. Using the concepts of boundary objects and trading zones, we trace the processes of collaborative research around sensor technology development and adoption within CENS. Over the 10-year lifespan of CENS, sensor technologies, sensor data, field research methods, and statistical expertise each emerged as boundary objects that were understood differently by the science and technology partners. We illustrate how sensing technologies were incompatible with field-based environmental research until researchers “unearthed” their infrastructures, explicitly reintroducing human skill and expertise into the data collection process and developing new collaborative languages that emphasized building dynamic sensing systems that addressed human needs. In collaborating around a dynamic sensing model, the sensing systems became embedded not in the environment of study, but in the practices of the scientists. Status and citation: This is the revised and accepted version, prior to publisher’s copy editing. Please quote the final version: Mayernik, Matthew S., Wallis, Jillian C., & Borgman, Christine L. (In press). Unearthing the infrastructure: Humans and sensors in field-based scientific research. Journal of Computer Supported Cooperative Work. doi: 10.1007/s10606-012-9178-
Fault plane of the 1964 Niigata earthquake, Japan, derived from relocation of the mainshock and aftershocks by using the modified joint hypocenter determination and grid search methods
The earthquake swarm of february 1981 in Mexico City
Entre el 4 y el 15 de febrero de 1981 ocurrió en la Cd. de México una serie de temblores particularmente bien registrados. Los 5 eventos mayores aquí analizados (2.7 <ML<3.2) tuvieron hipocentros dentro de un volumen de 1 km3, con localización media en 19.3780N - 99.196°W y una profundidad de 1.2 km. Las localizaciones relativas de estos eventos mostraron una migración de 0.7 a 1.6 km en un piano casi vertical. Se obtuvo una solución de piano de falla normal con el eje tensional en la dirección casi Este-Oeste, usando estaciones locales y regionales. El análisis espectral dio momentos sísmicos en el rango 0.5 - 2.0 x 1020 dinas-cm y caídas de esfuerzo de 1 a 5 bares. Se obtuvieron parámetros similares para el evento mayor ocurrido en una serie de temblores en la misma área en febrero de 1980. Parece ser probable que estos eventos ocurran como resultado de la acumulación de tensión regional; no obstante, el hundimiento del Valle de México podría posiblemente originar tensiones orientadas similares, las cuales, si no ocasionan los sismos, los pudieran disparar.
doi: https://doi.org/10.22201/igeof.00167169p.1982.21.2.90
- …