Reassessing the earthquake threat to San Francisco

This resource provides an abstract. New research suggests that authorities may need to reassess the threat posed by the Hayward fault, the fault responsible for San Francisco's highly destructive 1868 earthquake. The authors used a large shaking vehicle to send vibrations into the ground along a 1.6 kilometer portion of the Hayward fault and used the recorded vibrations reflected back from the fault to develop a profile of its shape and location. Findings are described.

Cracks from a Japanese earthquake heal in two years

This resource provides an abstract. Seventeen years of shockwave recordings were used to investigate crack healing after the large March 1997 Tokai region earthquake in Japan. Recordings taken at two stations in Japan from 1986 to 1996 were of shockwaves generated by other earthquakes, which passed through the crust region damaged by the 1997 Tokai quake. Comparing the observations taken before the earthquake to those taken afterwards, the researchers determined that the cracks healed in about two years, a finding similar to that of previous studies of crack repair.

Molten rock makes big earthquakes bigger

This resource provides an abstract. A modified friction welding device was used to spin one small cylinder of granite against another at high speed and pressure in order to simulate two plates sliding against each other. The velocity of the spinning granite cylinders, the force with which they were pushed together, and the temperature at their interface were measured. It was found that high heat generated when large plates slip against each other melts rock which accelerates slipping and results in more violent shaking than expected.

Magma shakes up earthquake locations

Numerical models were employed to examine the relationships between the orientation of volcanotectonic faults and magma movement. It was found that the direction of movement on strike-slip faults should be opposite to that predicted on the basis of regional stresses. The results do not explain the location of some volcanotectonic earthquakes and that the locations of preexisting faults may be more important in influencing the location of these earthquakes.

Improving earthquake warning in Costa Rica

This resource provides an abstract. This study examines seismic waves from a segment of the Middle America subduction zone below Central America that are capable of producing strong earthquakes. Results confirmed the depth of the crust-mantle boundary and mantle seismic velocities in the region. It was found that decreased seismic velocities are evidence that fluid affected nearly 15-25 percent of the mineral structure, leading to serpentinization. This data can contribute to improving earthquake hazard estimates for the area.

Stopping stick-slip seismic events?

This resource provides an abstract. This study models underground frictional resistance in stick-slip seismic events in order to determine the amount of energy needed to weaken a fault plane enough to initiate ground motion and simulate the speed of the recovery after the pressure subsides. The exact moment the slip began the maximum speed of the ground motion were detected. Results indicate that stick-slip events stop spontaneously when frictional melting begins, suggesting a potential way to stop the seismic events.

Using GPS for earthquake imaging

This resource provides an abstract. The authors used a dense array of Global Positioning System (GPS) stations to model how the Earth slipped during the 2003 8.0-magnitude Tokachi-Oki earthquake near Japan. Results indicate that displacements of more than one meter occurred in approximately 20 seconds on Hokkaido. It was found that while satellite data are less precise than traditional seismic data, GPS has the advantage in measuring displacement since seismometers cannot distinguish between the ground's acceleration and rotation.

Simplified modeling method to estimate lava flow

This resource provides an abstract. A numerical model that produces early predictions for the projected path of a lava flow was created. The two dimensional model is based on a generalized set of equations to describe lava flow propagation. Using real data from the 1991 1993 Mount Etna eruption in Italy, the model effectively reproduced the actual lava flow. This preliminary result indicates the usefulness of this method for forecasting lava flow paths for risk mitigation and predicting the damage from future eruptions.

Discover Our Earth

Discover Our Earth contains a wide range of information related to Earth science using graphs, maps, and movies. The focal topics are earthquakes, volcanoes, topography, plate tectonics, and sea level change. There are three main areas to access the data: Educators, Students, and Web Tools. The Educators section is designed to provide teachers with basic background information about selected Earth science topics and suggest several student activities and exercises that can be employed in classroom settings. Educators are encouraged to adopt, adapt, and modify exercises to suit their needs or situation. The Students section provides critical background information and primarily prepares students to start using the web tool QUEST (Quick Use Earth Science Study Tool). Using QUEST, students are able to experiment and test their own ideas and hypotheses related to any topics provided in these pages. With the tools and information provided, students are able to actively engage in an earth science knowledge discovery, critically evaluate the data and results, and reach their own conclusions about the earth system processes. Two Java-based, interactive data analyses and mapping tools allow customized access to a large variety of earth science data sets that are used by research scientists. The first Java applet, QUEST, has been designed and developed to be used by beginning and intermediate level earth science students. It has an easy-to-use interface that allows access to key earth science data sets. The second Java applet, GEOID (Geoscience Interactive Data tool), is more appropriate for advanced users, and provides a dynamic mapping interface and can be used to access all of the underlying earth science data sets.

Climate Monitoring and Diagnostic Laboratory: Carbon Cycle Greenhouse Gases

The National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostic Laboratory Carbon Cycle Greenhouse Gases group makes ongoing discrete measurements from land and sea surface sites and aircraft, and continuous measurements from baseline observatories and tall towers. These measurements document the spatial and temporal distributions of carbon-cycle gases and provide essential constraints to our understanding of the global carbon cycle. This website is an interactive atmospheric data visualization tool. This tool enables users to view data, obtain details about sampling locations, manipulate and compare data sets and create custom graphs. Data includes information on a variety of gases, and can be viewed as seasonal patterns, time series, or latitudinal distribution.