Tomographic imaging problems are typically ill-posed and often require the use of regularization techniques to guarantee a stable solution. Minimization of a weighted norm of model length is one commonly used secondary constraint. Tikhonov methods exploit low-order differential operators to select for solutions that are small, flat, or smooth in one or more dimensions. This class of regularizin...

ABSTRACT EM Cyg is an eclipsing dwarf nova with orbital period above the gap of cataclysmic variables. Based on whole outburst observed by Transiting Exoplanet Survey Satellite (TESS) from 2019 July 18–August 14, evolution quasi-periodic oscillations (QPOs) in was investigated. A QPO a about 1000 s found during both and quiescence. In addition, we another 500 s, which present but disappeared as...

Abstract Based on the linear traveltime interpolation (LTI) algorithm, we propose an improved LTI (referred as ILTI) algorithm for multiphase seismic ray tracing, which uses a velocity node in model parameterization and introduces secondary nodes between adjacent nodes. To better fit undulating surface model, irregular is used near interface, regular are still region far away from interface. We...

Applied to unmigrated data, the Common-Reflection-Surface (CRS) method is able to produce high-quality stacked sections, as well as useful traveltime parameters for a number of imaging and inversion purposes. One difficulty of the CRS method is the treatment of diffractions, especially when located close to reflections, and also triplications. In these regions, the CRS parameters obtained by co...

S U M M A R Y We present a significant addition to the data set of traveltimes of seismic PKP waves that sample the Earth’s lowermost mantle and core along the Earth’s rotation axis. Recorded at permanent Global Seismic Network (GSN) and temporary SSCUA deployment broadband seismographic stations in Antarctica, the new data improve the previously poor and biased coverage that underlies the seis...

S U M M A R Y We report on more than 100 earthquake waveform doublets in five subduction zones, including an earthquake nest in Bucaramanga, Colombia. Each doublet is presumed to be a pair of earthquakes that repeat at essentially the same location. These doublets are important for studying earthquake physics, as well as temporal changes of the inner core. Particularly, our observation from one...

Time-lapse geophysical measurements and seismic imaging methods in particular are powerful techniques for monitoring changes in reservoir properties. Traditional time-lapse processing methods treat each dataset as an independent unit and estimate changes in reservoir state through differencing these separate inversions. We present a general least-squares approach to jointly inverting time-varyi...