Low-velocity zone under long valley as determined from teleseismic events

Deep structure of Japan subduction zone as derived from local, regional, and teleseismic events

We have determined a detailed three-dimensional P wave velocity structure of the Japan subduction zone to 500-km depth by inverting local, regional, and teleseismic data simultaneously. We used 45,318 P wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the Japan Islands. The arrival times are recorded by the Japan University Seismic Network which covers the entir...

Resolving a low-velocity zone with surface-wave data

S U M M A R Y The main purpose of seismic inversion is the retrieval of seismic velocities and densities in the earth. Inversion of body-wave traveltimes cannot uniquely determine the seismic velocities as a function of depth when a low-velocity layer is present. It is generally assumed that surface waves do not suffer from the same non-uniqueness. The issue is addressed whether it is possible ...

Mega ultra low velocity zone and mantle flow

Mantle flow in Earth’s interior has been inferred from a variety of geo-disciplines. Two continentalscale, nearly antipodal, large low shear velocity provinces (LLSVPs) at the base of the mantle, thought to be dense and chemically distinct likely play a significant role in mantle dynamics and plume generation, and hence are targeted in a high-resolution seismic study. We analyze broadband SPdKS...

Teleseismic Time Functions for Large, Shallow Subduction Zone Earthquakes

Broadband vertical P-wave records are analyzed from 63 of the largest shallow subduction zone earthquakes which have occurred in the circum-Pacific in the last 45 yr. Most of the records studied come from a common instrument, the Pasadena, California, Benioff 1-90 seismometer. Propagation and instrument effects are deconvolved from the P-wave records using a damped least-squares inversion to ob...

Geochronology of the Long Valley Caldera as related to the Long Valley magma chamber