4 research outputs found
Astroclimate at San Pedro M\'artir I: 2004-2008 Seeing Statistics from the TMT Site Testing Data
We present comprehensive seeing statistics for the San Pedro M\'artir site
derived from the Thirty Meter Telescope site selection data. The observations
were obtained between 2004 and 2008 with a Differential Image Motion Monitor
(DIMM) and a Multi Aperture Scintillation Sensor (MASS) combined instrument
(MASS--DIMM). The parameters that are statistically analised here are: whole
atmosphere seeing -measured by the DIMM-; free atmosphere seeing --measured by
the MASS--; and ground-layer seeing (GL) --difference between the total and
free-atmosphere seeing--. We made a careful data coverage study along with
statistical distributions of simultaneous MASS--DIMM seeing measurements, in
order to investigate the nightly, monthly, seasonal, annual and global
behaviour, as well as possible hourly seeing trends. Although this campaign
covers five years, the sampling is uneven, being 2006 and 2007 the best sampled
years in terms of seasonal coverage. The overall results yield a median seeing
of 0.78 (DIMM), 0.37 (MASS) and 0.59 arcsec (GL). The strongest contribution to
the whole atmosphere seeing comes, therefore, from a strong ground layer. We
find that the best season is summer, while the worst one is winter, in
accordance with previous studies. It is worth noting that the best yearly
results are correlated with the best sampled years. The hourly analysis shows
that there is no statistically significant tendency of seeing degradation
towards dawn. The seeing values are slightly larger than those reported before.
This may be caused by climate changes.Comment: Accepted for publication (2012 June 14) in MNRAS, 15 pages, 16
Figures, 8 Table
Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals
Prior to major earthquakes many changes in the environment have been documented. Though often subtle and fleeting, these changes are noticeable at the land surface, in water, in the air, and in the ionosphere. Key to understanding these diverse pre-earthquake phenomena has been the discovery that, when tectonic stresses build up in the Earth’s crust, highly mobile electronic charge carriers are activated. These charge carriers are defect electrons on the oxygen anion sublattice of silicate minerals, known as positive holes, chemically equivalent to O− in a matrix of O2−. They are remarkable inasmuch as they can flow out of the stressed rock volume and spread into the surrounding unstressed rocks. Travelling fast and far the positive holes cause a range of follow-on reactions when they arrive at the Earth’s surface, where they cause air ionization, injecting massive amounts of primarily positive air ions into the lower atmosphere. When they arrive at the rock-water interface, they act as •O radicals, oxidizing water to hydrogen peroxide. Other reactions at the rock-water interface include the oxidation or partial oxidation of dissolved organic compounds, leading to changes of their fluorescence spectra. Some compounds thus formed may be irritants or toxins to certain species of animals. Common toads, Bufo bufo, were observed to exhibit a highly unusual behavior prior to a M6.3 earthquake that hit L’Aquila, Italy, on April 06, 2009: a few days before the seismic event the toads suddenly disappeared from their breeding site in a small lake about 75 km from the epicenter and did not return until after the aftershock series. In this paper we discuss potential changes in groundwater chemistry prior to seismic events and their possible effects on animals
Some observations of atmosferic luminosity as a possible earthquake precursor
Algunas mediciones de radiación solar obtenidas en la ciudad de México indican que pueden producirse valores anormales varios dÃas antes de un sismo fuerte. Las anomalÃas se presentan tanto en la parte verde como en la roja del espectro. Las emisiones parecen ser intermitentes y se traducen en una mayor varianza de la intensidad horaria medida en el actinómetro. Antes y después del sismo de Petatlán, .México del 14 de marzo de 1979 (M7.4), se observaron fuertes fluctuaciones en la luminosidad del cielo. En algunos casos la intensidad de la radiación excedió el valor esperado para una atmósfera transparente. Se propone que las observaciones altas se deben a una radiación en el espectro visible que se origina en la tierra, y que es reflejada por la capa de nubes y por la contaminación atmosférica.
doi: https://doi.org/10.22201/igeof.00167169p.1996.35.4.53