The concepts of forward modeling and inverse modeling

Provenance: Lee Slater, Rutgers University-Newark
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This unit introduces the student to the concept of geophysical inversion, which is the process of estimating the geophysical properties of the subsurface from the geophysical observations. The basic mechanics of the inversion process used to estimate spatial variations in electrical conductivity from electrical imaging (EI) datasets are introduced in a way that avoids the heavy mathematics. The challenges of inverting two dimensional geophysical datasets and the strategies for limiting the inversion to geologically reasonable solutions are described. The unfortunate characteristics of geophysical images (blurriness, imaging artifacts) are explained to highlight the limitations of inversion and to emphasize that the inverted images never match with geological reality. Students use the Excel-based Scenario Evaluator for Electrical Resistivity (SEER) tool introduced in Unit 3, Field Geophysical Measurements, to investigate key inversion concepts associated with measurement errors and the benefits of adding boreholes to surface data using synthetic datasets. Students are then led through an inversion of the two-dimensional EI dataset acquired in Harrier Meadow using ResIPy, a Python-based graphical user interface developed for instructional use. Following the instructional video, students then perform the inversion in ResIPy themselves and explore how variations in inversion settings related to the errors in the measurements result in distinctly different images.

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Students are introduced to evapotranspiration (ET) and how ET varies with meteorological factors and plant factors. A pre-class video and worksheet introduce students to estimating landscape water needs from ET and precipitation data. In class, students design low water-use landscaping and calculate the water savings of water-efficient landscaping compared with turf grass.

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The assignment is to calculate an annual water balance for a tree using data gathered at the Southern Sierra Critical Zone Observatory. In the framework of experimental design, students will organize around a research question "Is there enough water in the soil to account for transpiration?" After gathering and organizing data, students will calculate the annual water fluxes and reservoirs using a mass balance approach. Later these lessons can be expanded to catchment-scale calculations.

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The 2014 South Napa earthquake was the first large earthquake (Mag 6) to occur within the Plate Boundary Observatory GPS network since installation. It provides an excellent example for studying crustal strain associated with the earthquake cycle of a strike-slip fault with clear societal relevance. The largest earthquake in the California Bay Area in twenty-five years, the South Napa earthquake caused hundreds of injuries and more than $400 million in damages. This activity uses a single triangle of GPS stations (P198, P200, SVIN), located to the west of the earthquake epicenter, to estimate both the interseismic strain rate and coseismic strain. By the end of the exercise, the students also have direct evidence that considering the recurrence interval on a single fault, which is part of a larger system, is not reasonable. An extension option gives the opportunity to discuss earthquake early warning systems.

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Note: Although the term GPS (Global Positioning System) is more commonly used in everyday language, it officially refers only to the USA's constellation of satellites. GNSS (Global Navigation Satellite System) is a universal term that refers to all satellite navigation systems including those from the USA (GPS), Russia (GLONASS), European Union (Galileo), China (BeiDou), and others. In this module, we use the term GPS even though, technically, some of the data may be coming from satellites in other systems.

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Online-ready: The exercise is electronic (including accessing an online data portal) and could be done individually or in small online groups. Lecture can be done in synchronous or asynchronous online format.

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This is the second module of a two week-long unit on hydrology in an upper-level undergraduate course on the Critical Zone. After Unit 5.1, students should have a basic understanding of the fluxes and reservoirs in the context of a tree and basin water balance. In Unit 5.2, students will learn how to apply environmental sensor data to larger catchment or regional scales (Part 1) and will connect hydrologic processes in the Critical Zone to societal needs through a quantitative resource availability and decision-making exercise (Part 2).

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In this two-day activity, students monitor an evolving volcanic crisis at a convergent plate boundary (Cascadia). Using monitoring data and geologic hazard maps, students make a series of forecasts for the impending eruption and associated risks. By the end of the activity, students will have learned the outcome of the eruption and assess the impacts of the eruption of Mount Rainier on specific locations around the volcano.
This unit begins by having students examine past volcanic eruptions at Mount St. Helens, associated with the Cascadia convergent plate boundary, through firsthand accounts by United States Geological Survey (USGS) personnel who describe their work monitoring the geologic activity and some associated impacts. During class on the first day (Unit 5), students will begin working in small groups to interpret one of three data sets used to monitor volcanic activity (seismic, gas and ash emissions, and tilt). During prework and in-class activities for day 2 (Unit 6), students will update their predictions by combining information from all three data sets in mixed groups in which students act as "experts" for a particular data set. The exercise culminates with students assessing the impacts of a simulated volcanic eruption at their assigned locations.

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This unit addresses changes in hurricane risks due to coastal development. Students will calculate the risks from hurricanes and how the hazards have changed (or not) from 1901 to 2010. Students will determine how changes in coastal development have altered the risks presented by hurricanes by analyzing data in Activity 5.1 and historic maps and aerial photographs in Activity 5.2.

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Screenshot of the slider tool used to relate geophysical images to vegetation pattern

Provenance: Lee Slater, Rutgers University-Newark
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In this unit, students explore spatial associations between the three-dimensional electromagnetic (EM) conductivity inversions and the visible patterns of Salicornia (Pickleweed) introduced in Unit 1, Exploring Harrier Meadow. The Arcview Storymap started in Unit 1 allows students to overlay inverted electrical conductivity patterns for different depths on aerial photographs of Harrier Meadow that highlight the patches of Pickleweed. Students analyze how conductivity patterns vary with depth and explore for evidence for a relationship between electrical conductivity and Pickleweed patches based on the hypothesis introduced in Unit 1. Students then perform an integrated interpretation of both the EM and electrical imaging inversions along with the results of direct sampling (coring, pore water sampling, soil characterization) conducted at locations selected using the electrical conductivity patterns observed in the EM dataset. Students perform basic qualitative assessments of the correlation between physical and chemical properties of the sampled soils and soil electrical conductivity from the EM inversions. Students finish the module by evaluating the extent to which the geophysical dataset and supporting direct measurements support the hypothesis pertaining to the cause of the Salicornia clusters introduced in Unit 1.

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Students will examine data that record the modern increase in carbon dioxide concentrations and the associated increase in average temperatures, and they will investigate the effects of carbon dioxide on various components of the Earth system (atmosphere, cryosphere, hydrosphere -- oceans). Students also learn how the burning of fossil fuels contributes to increases in atmospheric carbon dioxide.

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Unit 5 addresses the concept of Net Zero Water of buildings. Net Zero Water can be defined in different ways. For this module it means a building's water needs are supplied 100% from harvested rainwater or water that is recycled on site. Reducing indoor and outdoor water use is a key element. Reading and videos are assigned to aid students grasping the concept of Net Zero Water as applied to buildings. A spreadsheet tool from the U.S. Green Building Council is introduced and used to estimate indoor water demand for baseline and design (water conservation) scenarios. In addition, this unit links to Unit 4 by including an estimate for outdoor water demand. The central activity for the unit is an active learning team exercise to analyze indoor water use reduction for a case study building and evaluate Net Zero Water.

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Students will review current ocean pressures related to overfishing and human impacts on ocean ecosystems. By examining data collected in relation to the presence of marine reserves, students will explore long-term strategies for protecting ocean resources. Students will review scientific data to assess biomass, biodiversity, and reproductive success of fishery stocks in a marine protected area (MPA) and propose a location for the establishment of a marine reserve in the Channel Islands, California.

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Is sea level change globally uniform? How do sea level changes have the potential to influence major metropolitan areas during the next century? How should these changes be addressed, and who should be responsible for taking action? In this unit, the conclusion to the Ice Mass and Sea Level Change module, students explore the potential impacts of sea level change on the economy, infrastructure, and residents of Southern California and New York City. Students also consider how changes in these two regions will have a widespread influence on other US cities, even for landlocked communities.

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Online-adaptable: This sea level impact analysis is designed to be done in small groups and possibly with a class gallery walk. These would need to be converted to small online groups and online discussion. The Part 4 wall walk could potentially be adapted to class discussion that uses polling feature to see people's opinions. Arguments could be made verbally or with the chat box.

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Unit 5 is the summative assessment for the module. This final exercise takes eight to ten hours. The exercise evaluates students' developed skills in survey design, execution of a geodetic survey, and simple data exploration and analysis. This summative assessment is written flexibly so that it can be applied to a variety of potential field sites and associated geoscience research questions. The unit has two parts, like most of the units in the module: Part 1, Geodetic Survey; and Part 2, Data Exploration. In addition, there is an optional Part 3, Data Processing, for students who have done Unit 4. This unit also has a number of prepared data sets for courses not able to collect field data.

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In this unit, students will learn about the dynamic movement of nutrients among and within ecosystems primarily through the reading and discussion of scientific literature. This unit is generally subdivided into three sections: (1) allochthonous inputs (2) the role of organisms in biogeochemical cycles and how ecological theory can be applied to biogeochemistry and (3) how biogeochemical processes can assist in creating solutions for humanity's grand challenges. This unit is designed to provide students with the opportunity to develop their reading and interpretation of scientific literature. Students will also become familiar with the utility of isotopic techniques and their use in biogeochemistry through readings and data analysis of carbon and nitrogen isotopic data sets. Chosen scientific articles are provided, each with their own set of reading questions. Additionally, short introductory materials are provided to introduce students to some of the general concepts and processes in the study of biogeochemistry.

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In this week-long unit students will explore Critical Zone function and dynamics as they relate to nutrient cycling in agricultural systems and nutrient pollution into aquatic systems. This unit is generally subdivided into three sections: (1) nutrient pollution (2) agricultural importance and (3) Critical Zone function and dynamics in relation to nutrient cycling. The students will use data sets, interactive activities, primary literature, and videos to allow them to examine the role that the CZ plays and how that role changes with differing land uses. Important present-day topics of food production, clean water, nutrient pollution, and sustainable agriculture are examined using a CZ lens. Students will interact with each other on a variety of scales (individual, small groups, entire class) and using a variety of modes (presentations, written reports, question and answers, and class discussion) in this unit. Additionally, optional activities are provided if lab activities are able to be accommodated. The unit ends with a summative assessment assignment that is based on an innovative call for proposals to combat one of America's most widespread, costly, and challenging environmental problems: nutrient pollution.

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Students select their own set of three stations in an area of interest to them, conduct a strain analysis of the area between the stations, and tie the findings to regional tectonics and societal impacts in a 5 -- 7 minute class presentation. For many students this is their first foray into "research" and can be a powerfully eye-opening and exciting (if intimidating) experience. In larger classes, students can work in pairs to shorten total time needed for presentations. Unit 6, along with exam question/s, is the Summative Assessment for the module.

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Online-ready: The exercise is a final project that can be done remotely, individually or in small online groups. Final presentations could be done in a synchronous class period.

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In this unit, students address the issue of groundwater demands and environmental justice in the arid Southwest, a region with some of the largest percentages of Hispanics and Latinos in the United States. Students discuss the Rule of Capture, the overuse of water resources, and the dwindling supply of groundwater in many parts of the Ogallala Aquifer. Students connect groundwater's role to the hydrological cycle and consider how issues of inequity can occur when groundwater is not properly regulated.

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In this two-day activity, students monitor a simulated evolving volcanic crisis at a convergent plate boundary (Cascadia). Using monitoring data and geologic hazard maps, students make a series of forecasts for the impending eruption and associated risks. By the end of the activity, students will have learned the outcome of the eruption and assess the impacts of the eruption of Mount Rainier on specific locations around the volcano.
This unit is a continuation of Unit 5, in which students analyzed simulated pre-eruption seismic, tilt, and gas emission data. In this, the second day of the simulation, students update their eruption forecasts based on new data (in the prework) and then (in groups in class) by combining information from multiple data sets. In class, each group assesses the vulnerability of one or more assigned locations near Mount Rainier. The exercise culminates with students assessing the impacts of the simulated eruption at their assigned locations.

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Unit 6 covers the preliminary design of a rainwater harvesting unit. Pre-class assignments provide background on rainwater harvesting. An active learning exercise steps student teams through the process of sizing a rainwater harvesting cistern, using water demand estimates from Units 4 and 5. The activity leads into a revision of the water system mind map developed in previous units.

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Picture of urban flooding

Provenance: Timothy Swinson https://commons.wikimedia.org/wiki/File:Trapped_woman_on_a_car_roof_during_flash_flooding_in_Toowoomba_2.jpg
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Unit 8 covers the basics of hydroclimatic extreme events with a focus on floods and droughts. Topics include introduction to floods and droughts, impact of urbanization on extremes, how to understand and predict extremes, how to tackle them (management strategies), and elements of urban climate resilience. The teaching strategy is designed with short and divided lectures filled with discussion questions and a group activity. Students will be working with time series flow data for statistical analysis of extreme events.

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