Amphibious Array

We propose to use an array of ocean bottom seismometers to study the Cascadia subduction zone off of the west coast of Oregon and Washington. The motivation for selecting this region for the project is because it is an area where episodic tremor and slip is known to occur.  One of the reasons that it is important that we study this area is that there are millions of people that live in this region and it is geologically active with volcanoes and faults, yet we still do not have a great understanding of the geology here.  Another reason that this project is important is the fact that ocean bottom seismometers provide us with extremely poor data quality, which means that the methods developed on this data should be applicable to ocean bottom data that has been gathered from other regions around the globe.  This is also important because dropping seismometers into the ocean without making boreholes happens to be the least expensive way to deploy ocean bottom seismometers. The main goals of this project are to better constrain the boundary between the oceanic and continental crust, the structure of the oceanic crust in the outer rise, and to better locate and measure the intensity of episodic tremor and slip.  In order to do this, we need to improve the methods that are currently used to remove noise because ocean bottom data is typically the lowest quality data in the field of seismology, which typically makes interpretations of waveforms difficult.  Another goal of this proposal is to develop new methods for removing this noise from ocean bottom data that can be generalized to most ocean bottom data, and the current methods are not sufficient to make this data useful.  The last goal of the project is to characterize the variations of elastic properties in the crust and mantle lithosphere across Cascadia and the Pacific-North American plate boundary.  We will be using traditional methods to locate earthquakes and employing receiver function methods with improvement upon the most recent techniques of removing noise to make the worst quality data practical to use in the field of seismology.  This effort will have broad impacts on the field as a whole because it will allow us to obtain new knowledge about the geology in Cascadia, the Cascadian subduction zone, and the structures of the outer rise of the oceanic crust.  It will also allow for new methods of improving seismic data to be created that can be applied to many projects dealing with ocean bottom data, which is a practice that has not yet been mastered or even made practical for the most part.    

Lithium composition equation

Darcy's Law

P Wave and S Wave Velocity

Manning's Equation

Famine and Feast: Recent Changes to the Global Nitrogen Cycle

The global human population exploded from 1.5 to over 7 billion during the last century. By the middle of the century, the need for increased of crop production was urgent order to meet the growing demand for food. The invention of synthetic nitrogen fertilizer, coined the ‘Green Revolution’ achieved this goal. Crop yields, or the amount of food produced on a given piece of land, increased by 30% globally, saving many people from starvation. So much nitrogen has been added to the fields since then, however, that much has leaked out into streams, lakes, and estuaries and caused major pollution problems that jeopardize human health and the economic value of fisheries. After drastically altering the global nitrogen cycle to relieve a shortage, society is now grappling with an overabundance. My own research seeks to understand how to remove excess nitrogen from watersheds and remediate the issues related to over-fertilization. 

Nitrogen is the most abundant element in Earth’s atmosphere, yet millions of dollars are spent manufacturing nitrogen-based fertilizer every year. What drives this lucrative industry? The answer is the form of nitrogen in the atmosphere. Nearly 80% of the atmosphere is composed of pure nitrogen gas, which is un-useable to most plants. Harnessing nitrogen from the sky requires a lot of energy. The Haber-Bosh process uses man-made energy (oil, gas, nuclear power) to add hydrogen atoms to nitrogen gas, creating massive amounts of ammonia. Some of this ammonia may end up in household cleaning products, but most is used as fertilizer.

Of course, humans did not invent this process. Several different types of bacteria and algae have special enzymes that allow them to harvest nitrogen from the sky at low temperatures, without the excess energy that the Haber-Bosh process requires. A small number of plants (mostly peanuts and beans, and some common flowers) formed alliances with these bacteria, allowing them to live in tiny holes in their roots. These plants enjoy the advantage of abundant nitrogen, and microbes accept a safe place to live and a small share of the sugary products of photosynthesis in return.

The majority of plants are not so lucky to cohabitate with nitrogen harvesting bacteria. Instead, nitrogen is only available as a recycled organic matter – broken down leaves, wood, or animal scat. For the entire history of plants the small number of organisms controlled the abundance of bio-available nitrogen in the world, and whole ecosystems organized around the principle of recycling. Agricultural fields played by the same rules, and farmers had to carefully recycle crop and animal waste in order conserve nutrients in the soil.  

Haber-Bosh tipped this natural balance. While this invention revolutionized agriculture and increased crop yields around the world, many natural, non-agricultural ecosystems were fertilized in the process. Aquatic ecosystems, especially estuaries, are particularly sensitive to fertilization and respond with a flurry of algae growth. Fertilized algae in an estuary grow like weeds in a garden, choking out other life forms such as fish, mollusks, and even crabs. This phenomenon, known as a Dead Zone, happens regularly in many coastal zones today.

The Haber Bosh process has doubled the rate of nitrogen fixation from atmosphere to land. This excess has shown up in water bodies and caused major ecological problems. 

Dead zones present a major challenge for managing chemical cycles globally. Human activities have doubled the rate of nitrogen fixation since 1950, and synthetic fertilizer is still widely applied to agricultural fields, despite widespread impacts on ecosystems. Unfortunately there is no mechanized process to convert ammonia back to nitrogen gas. Certain microbes can convert ammonium back into nitrogen gas. This process is very slow compared to the Haber-Bosh process, though. Significant progress has been made to mitigate nitrogen pollution in certain critical regions, however. In the past twenty years, efforts to curb agricultural fertilizer applications have reduced pollution. Scientists such as myself have dedicated entire careers to studying the bacterial communities that remove nitrogen from waterways. One way to remove nitrogen is to create or restore wetlands where these bacteria live and provide the conditions necessary for rapid nitrogen removal. Widespread implementation of different ecosystem restoration practices has potentially curbed the load of nitrogen entering the Chesapeake Bay, for instance.

Are Increasing Flood Losses Due to Climate Change?

Federal aid in response to the damage caused Hurricane Sandy currently amounts to over $60 billion dollars, while total economic damage will likely be over $80 billion dollars. This follows just a year after 2011’s Hurricane Irene and tropical storm Lee, which caused damages of over $16 billion. Much of the damage caused by these storms was due to extensive flooding from the large amounts of rain delivered by the storms. Figures from the National Weather Service show an increasing trend in flood damages in recent decades.

The consensus within the scientific community, and increasingly in the public opinion, is that climate change is causing more frequent and intense storm events. But climate change is not the whole story behind the increase in economic costs from storms. A significant factor behind increased losses from floods is that more people live in high-risk areas such as floodplains and coastal areas. A related cause is that the value of our assets has increased in the past several decades. To illustrate this, compare the value of everything you own in your house to what your grandmother would have owned at your age.

Why have we allowed so much development in high-risk areas? Ironically, much of the reason is because of federal policy originally designed to reduce the cost of flood damages. The National Flood Insurance Program was established in 1968 in response to rising concern over the amount of federal aid given to victims of floods. The program mandated flood insurance for homeowners in designated high-risk areas. The standard chosen for delineating these high-risk areas was the “100-year” flood.

The “100-year” flood is a term that is often misunderstood, because it does not refer to the flood that only occurs once every hundred years. Rather, it is the magnitude of flood that has a 1% chance of occurring in any given year. Stated another way, over a very long period of time, this is the magnitude of flood that would occur on average every 100 years.

Hydrologists determine the magnitude of the “100-year” flood at a given location by using available streamflow data from the U.S. Geological Survey. Hydrologists assume that the chance of a future flood of a certain size will be the same as the chance that size flood occurred in the past, which can be estimated using the streamflow data. This method assumes the conditions causing floods in the pasts will be the same as future conditions. There are two major problems with this assumption. The first is that the watershed and stream channel may not have stayed the same over time. In many places we have modified rivers by building dams (decreasing flood magnitude), and levees (decreasing flood risk locally but increasing flood magnitude downstream). Also, urbanization creates more impermeable surfaces, which increases the amount of runoff after storms and leads to larger floods.

As mentioned before, the frequency and intensity of storms is likely changing, such that the climatic conditions that led to flood events in the past will be different from those in the future. This means that the “100-year” estimates underlying the National Flood Insurance Program are not accurate reflections of true flood risk in many areas, and has led to inappropriate development in high-risk areas. Scientists such as myself are interested in better quantifying the relationships between climate and large floods in order to support improved risk management policies.