Hurricane intensification may be related to eyewall precipitation

This resource provides an abstract. The authors used weather surveillance radars along the United States coast to study the frequency of tall precipitation in order to quantify the relationship between hurricane wind intensification and tall precipitation cells along hurricane eyewalls. Their analysis showed that if the frequency of tall precipitation in the eyewall is at least 33 percent then there was an 82 percent chance that hurricane winds will intensify. If this threshold was not met, the chance of wind intensification dropped to 17 percent. The authors suggest that this height-frequency threshold could aid forecasters during future hurricane seasons.

Tsunami warnings using ocean circulation models

This resource is an abstract. This study uses numerical models that take advantage of digital seismometry and satellite radar altimetry to shed light on tsunami source and formation mechanisms. The authors used data from the 26 December 2004 tsunami to generate a 3-D ocean circulation model that they compared it to actual wave propagation recorded by satellites. It was found that the model consistently matches the observed phenomenon. The authors suggest that ocean-general-circulation-models coupled with fresh earthquake data can provide earlier warning to coastal communities at risk.

Listening to the 2004 Indian Ocean tsunami quake

This resource is an abstract. This study tracks the movement of the rupture that caused the December 26, 2004 Indian Ocean tsunami by comparing recordings of sound waves from five sensors located around the Indian Ocean. The data were used to triangulate the location of sound wave source. Results indicated that the rupture first moved northwest at 2.4 kilometers per second along the Sunda trench then slowed to 1.5 kilometers per second around 600 kilometers from the earthquake's epicenter. The author indicates that the slower speed of the rupture was unusual for an earthquake caused by a rupture close to the surface.

A tsunami warning system for the Indian Ocean

This resource is an abstract. Using tidal gauge data from the time of the 2004 Indian Ocean tsunami, the authors were able to reconstruct the height and speed of the waves and the time it took them to reach coastal regions. Readings from the tidal gauges could have given advance warning to some areas hit by the tsunami, had a warning system been in place. Suggestions for creating a tsunami warning system for the Indian Ocean region are given.

How volcanic eruptions cause tsunamis

This study investigates the effect of pyroclastic flows on tsunami generation. The authors analyzed several possible mechanisms that occur when the particle rich flows encounter water and conclude that the volume and density of the basal flow has a close correlation with the wave's amplitude and wavelength, which can be used to model the water movement in lakes, bays and oceans.

Predicting catastrophic earthquakes

This resource provides an abstract. This article discusses a method based on the magnitude-frequency distribution of previous earthquakes in a region. It is used to examine the probability of a small earthquake growing into a catastrophic one. When a small earthquake is detected in a region where a catastrophic one is expected, early warning systems can be modified to determine the probability that this earthquake will grow in magnitude. It was found that if the observed earthquake magnitude reaches 6.5, the estimated probability that the final magnitude will reach 7.5 is between 25 and 41 percent.

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.

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.