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-

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