Some thoughts on the use of InSAR data to constrain models of surface deformation: Noise structure and data downsampling

Repeat-pass Interferometric Synthetic Aperture Radar (InSAR) provides spatially dense maps of surface deformation with potentially tens of millions of data points. Here we estimate the actual covariance structure of noise in InSAR data. We compare the results for several independent interferograms with a large ensemble of GPS observations of tropospheric delay and discuss how the common approaches used during processing of InSAR data affects the inferred covariance structure. Motivated by computational concerns associated with numerical modeling of deformation sources, we then combine the data-covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling (or averaging). We illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum. For the larger events, our goal is to invert for the coseismic fault slip distribution. For smaller events, we infer the hypocenter location and moment. We compare the results of inversions using several different resampling algorithms, and we assess the importance of using the full noise covariance matrix

Nutrient Cycling In Tropical Grasses Irrigated With Dairy Effluent in a Tropical Island Environment

In Hawaii and other island environments, dairy producers accumulate large quantities of effluent in lagoons. These lagoons can potentially overflow causing the nutrients and other contaminants to pollute the land and associated water bodies. Alternative uses of effluent are urgently needed for a sustainable and environment-friendly dairy production. This study assessed the effects of effluent irrigation on plant and soil (Cumulic Haplustoll) properties. Five tropical grasses—bana {Pennisetum purpureum S.), California (Brachiaria mutica S.), signal (Brachiaria decumbens S.), star (Cynodon nlemfuensis V.) , and suerte (Paspalum atratum S.)—received subsurface drip irrigation of dairy effluent at two rates based upon the potential evapotranspiration (ETp) at the site (Waianae, Hawaii)—2.0 ETp (7 to 44 mm d"‘) and 0.5 ETp (2 to 11 mm d"*). No excessive increases in extractable soil P (81 to 176 mg kg'') and soil solution total P (3 to 9 mg L'') was observed after two years of effluent irrigation. Soil pH and soil solution pH fluctuated over time due to the high soil buffering capacity. Salinity and sodicity were not observed in this effluent-irrigated soil. Soil electrical conductivity (ECspc) declined from 18.0 dS m'' in July 2003 to 2.7 dS m * in Aug 2006—lower than the U.S. Salinity Laboratory’s critical level for classifying soils as saline (4.0 dS m''). Soil exchangeable sodium percentage (6.4 to 10.2%) remained below 15%—critical value critical value for classifying soils as sodic. Brachiaria mutica and P. purpureum yielded the highest dry matter of 57 and 53 Mg ha'' y ', respectively. Average nutrient removal of grasses was 30 to 187%, 13 to 86% and 2 to 14% of applied effluent N, P and K, respectively. Forage quality was within acceptable levels for feeding to dairy cattle. Modeling results showed that total applied phosphorus determines how many animals may be raised and how much area may be utilized to produce the forage. Results indicated that irrigating high yielding tropical grasses with effluent at 2.0 ETp was acceptable for recycling of nutrients from the effluent. Additional monitoring is needed to determine the longer-term impacts of effluent application on soil and plant properties

Some thoughts on the use of InSAR data to constrain models of surface deformation : noise structure and data downsampling

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q01007, doi:10.1029/2004GC000841.Repeat-pass Interferometric Synthetic Aperture Radar (InSAR) provides spatially dense maps of surface deformation with potentially tens of millions of data points. Here we estimate the actual covariance structure of noise in InSAR data. We compare the results for several independent interferograms with a large ensemble of GPS observations of tropospheric delay and discuss how the common approaches used during processing of InSAR data affects the inferred covariance structure. Motivated by computational concerns associated with numerical modeling of deformation sources, we then combine the data-covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling (or averaging). We illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum. For the larger events, our goal is to invert for the coseismic fault slip distribution. For smaller events, we infer the hypocenter location and moment. We compare the results of inversions using several different resampling algorithms, and we assess the importance of using the full noise covariance matrix.R. Lohman is partially supported by a NASA New Investigator Program grant award to M. Simons

Locations of selected small earthquakes in the Zagros mountains

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q03001, doi:10.1029/2004GC000849.The Zagros mountains of southern Iran are marked by a zone of high seismicity and accommodate a significant portion of the convergence between Arabia and Eurasia. Due to the lack of dense local seismic or geodetic networks, the inferred kinematics of the collision in Iran is mainly based on catalogs of teleseismically determined earthquake locations. We surveyed all M w > 4.5 earthquakes in the Harvard Centroid Moment Tensor (HCMT) and International Seismological Centre (ISC) catalogs that occurred in the Zagros mountains during the period 1992–2002 and that were spanned by Interferometric Synthetic Aperture Radar (InSAR) images from the ERS 1 and 2 satellites. We invert the observed deformation for the best fitting point source, single fault plane, and distributed fault slip for four earthquakes and one unexplained deformation event. We find that we can precisely locate earthquakes that are too small to be well-located by either the HCMT or ISC catalogs, allowing us to tie specific earthquakes to active geologic structures.ERS 1 and 2 data were acquired through an ESA category-1 proposal. R. Lohman is partially supported by a NASA New Investigator Program grant award to M. Simons

Facing alternative futures: prospects for and paths to food security in Africa

"Food security in Africa has substantially worsened since 1970. Although the proportion of malnourished individuals in Sub-Saharan Africa has remained in the range of 33–35 percent since around 1970, the absolute number of malnourished people in Africa has increased substantially with population growth, from around 88 million in 1970 to an estimate of over 200 million in 1999–2001. Yet this discouraging trend need not be a blueprint for the future. New research from IFPRI shows that the policy and investment choices of African policymakers and the international development community can make an enormous difference for Africa's future agricultural production and food security. By modeling the results of a number of different policy scenarios in Africa through the year 2025, we show that the number of malnourished children, one important indicator of food security, could rise as high as 41.9 million or fall as low as 9.4 million. These scenarios, therefore, shed light on the effectiveness of various policies and investments in assuring a food-secure future for Africa.' from TextFood insecurity, Forecasting, Agricultural productivity, Human capital, Malnutrition in children, Impact model,

Looking ahead: long-term prospects for Africa's agricultural development and food security

"Sub-Saharan Africa is the only developing region in the world where food insecurity has worsened instead of improved in recent decades. In this discussion paper, Mark W. Rosegrant, Sarah A. Cline, Weibo Li, Timothy B. Sulser, and Rowena A. Valmonte-Santos show that this discouraging trend need not be a blueprint for the future. The research contained in this discussion paper was conducted in preparation for the IFPRI 2020 Africa conference “Assuring Food and Nutrition Security in Africa by 2020: Prioritizing Actions, Strengthening Actors, and Facilitating Partnerships,” held in Kampala, Uganda, April 1–3, 2004. The authors examine the implications of several different policy scenarios based on IFPRI's International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT). This model, developed at IFPRI in the early 1990s, has been continually updated to incorporate more food sectors and geographic regions. In this paper, the authors use IMPACT to assess the consequences of a wide range of policy and investment choices for Africa, including a business as usual scenario (continuation of current policy and investment trends through 2025), a pessimistic scenario (declining trends in key investments and in agricultural productivity), and a vision scenario (improving trends in investments and hence in agricultural productivity and human capital), as well as scenarios for more effective use of rainfall in agriculture, reduced marketing margins, and three different scenarios for trade liberalization. The wide variation in results reveals how much these choices will matter. For example, the number of malnourished children under five years old in Sub-Saharan Africa in 2025 is projected to be 38.3 million under business as usual, 55.1 million under the pessimistic scenario, and 9.4 million under the vision scenario. It is our hope that this research will clarify the steps needed to help stimulate the actions contributing to approaching the vision scenario. " From Foreword by Joachim von BraunImpact model, Food insecurity, Forecasting, Agricultural productivity, Human capital, Malnutrition in children,

Designing Mobile Educational Games on Voter‟s Education: A Tale of Three Engines

The rapid growth of mobile learning is influenced by the ability to access learning content anytime and anywhere. The on demand capability is available because mobile devices allow for convergence of internet and communications technologies. At the same time, the availability of engines makes development of mobile applications faster and seamless. However, not all mobile development engines are alike. This paper discusses on the development of mobile learning applications using mobile development engines in teaching Filipinos on responsible voting. Specifically, this paper discusses how AndEngine, Ren’Py, and homegrown Usbong were used to develop a mobile board game and a mobile comic book to promote responsible voting to the Filipino youth

Relationships among seismic velocity, metamorphism, and seismic and aseismic fault slip in the Salton Sea Geothermal Field region

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 120 (2015): 2600–2615, doi:10.1002/2014JB011579.The Salton Sea Geothermal Field is one of the most geothermally and seismically active areas in California and presents an opportunity to study the effect of high-temperature metamorphism on the properties of seismogenic faults. The area includes numerous active tectonic faults that have recently been imaged with active source seismic reflection and refraction. We utilize the active source surveys, along with the abundant microseismicity data from a dense borehole seismic network, to image the 3-D variations in seismic velocity in the upper 5 km of the crust. There are strong velocity variations, up to ~30%, that correlate spatially with the distribution of shallow heat flow patterns. The combination of hydrothermal circulation and high-temperature contact metamorphism has significantly altered the shallow sandstone sedimentary layers within the geothermal field to denser, more feldspathic, rock with higher P wave velocity, as is seen in the numerous exploration wells within the field. This alteration appears to have a first-order effect on the frictional stability of shallow faults. In 2005, a large earthquake swarm and deformation event occurred. Analysis of interferometric synthetic aperture radar data and earthquake relocations indicates that the shallow aseismic fault creep that occurred in 2005 was localized on the Kalin fault system that lies just outside the region of high-temperature metamorphism. In contrast, the earthquake swarm, which includes all of the M > 4 earthquakes to have occurred within the Salton Sea Geothermal Field in the last 15 years, ruptured the Main Central Fault (MCF) system that is localized in the heart of the geothermal anomaly. The background microseismicity induced by the geothermal operations is also concentrated in the high-temperature regions in the vicinity of operational wells. However, while this microseismicity occurs over a few kilometer scale region, much of it is clustered in earthquake swarms that last from hours to a few days and are localized near the MCF system.This work was funded by USGS NEHRP proposal G10AP00101 and NSF proposal 0943906.2015-10-2