Simple and reliable finite fault solutions for large earthquakes using the W-phase: The Maule (M w = 8.8) and Tohoku (M w = 9.0) earthquakes

We explore the ability of W-phase waveform inversions to recover a first-order coseismic slip distribution for large earthquakes. To date, W-phase inversions for point sources provide fast and accurate moment tensor solutions for moderate to large events

Evaluation of the Performance Characteristics of the Lightning Imaging Sensor

The Lightning Imaging Sensor (LIS) that was on board the Tropical Rainfall Measuring Mission (TRMM) satellite captured optical emissions produced by lightning. In this work, we quantify and evaluate the LIS performance characteristics at both the pixel level of LIS events and contiguous clusters of events known as groups during a recent 2-yr period. Differences in the detection threshold among the four quadrants in the LIS pixel array produce small but meaningful differences in their optical characteristics. In particular, one LIS quadrant (Q1, X >= 64; Y >= 64) detects 15%-20% more lightning events than the others because of a lower detection threshold. Sensitivity decreases radially from the center of the LIS array to the edges because of sensor optics. The observed falloff behavior is larger on orbit than was measured during the prelaunch laboratory calibration and is likely linked to changes in cloud scattering pathlength with instrument viewing angle. Also, a two-season comparison with the U.S. National Lightning Detection Network (NLDN) has uncovered a 5-7-km north-south LIS location offset that changes sign because of periodic TRMM yaw maneuvers. LIS groups and flashes that had any temporally and spatially corresponding NLDN reports (i.e., NLDN reported the radio signals from the same group and/or from other groups in the same flash) tended to be spatially larger and last longer (only for flashes) than the overall population of groups/flashes.NASA [80MSFC17M0022]; NASA ROSES-2014 program [NNH14ZDA001N-WEATHER]6 month embargo; published online: 6 June 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Upper crustal structure of central Java, Indonesia, from transdimensional seismic ambient noise tomography

Delineating the crustal structure of central Java is crucial for understanding its complex tectonic setting. However, seismic imaging of the strong heterogeneity typical of such a tectonically active region can be challenging, particularly in the upper crust where velocity contrasts are strongest and steep bodywave ray paths provide poor resolution. To overcome these difficulties, we apply the technique of ambient noise tomography (ANT) to data collected during the Merapi Amphibious Experiment (MERAMEX), which covered central Java with a temporary deployment of over 120 seismometers during 2004 May-October. More than 5000 Rayleigh wave Green's functions were extracted by cross-correlating the noise simultaneously recorded at available station pairs. We applied a fully non-linear 2-D Bayesian probabilistic inversion technique to the retrieved traveltimes. Features in the derived tomographic images correlate well with previous studies, and some shallow structures that were not evident in previous studies are clearly imaged with ANT. The Kendeng Basin and several active volcanoes appear with very low group velocities, and anomalies with relatively high velocities can be interpreted in terms of crustal sutures and/or surface geological features

Numerical tsunami simulation including elastic loading and seawater density stratification

Systemic discrepancies between observed and modeled tsunami wave speeds were previously identified for two recent major tsunamis: the 2010 Maule and 2011 Tohoku events. To account for these discrepancies, we developed a numerical tsunami propagation cod

Shallow intraplate earthquakes in Western Australia observed by Interferometric Synthetic Aperture Radar

We investigate two intraplate earthquakes in a stable continental region of southwest Western Australia. Both small-magnitude events occur in the top ∼ km of crust and their epicenters are located with an accuracy of ∼100 m (1 σ) using satellite Int

Localization of intraplate deformation through fluid-assisted faulting in the lower-crust: The Flinders Ranges, South Australia

In this paper we present a hypothesis for localized, intraplate deformation in the continental crust of south-central Australia that involves fluid-assisted reactivation of faults in the mid- to lower crust. Using data from a temporary seismometer deployment in the Flinders Ranges, we show that earthquakes, relocated in a 3D velocity model, cluster in elongated low vp /. vs anomalies that extend to depths exceeding 20. km, and are aligned with the axis of the Flinders Ranges. In the northern Flinders Ranges these low vp /. vs anomalies can be interpreted as fractured Neoproterozoic to Cambrian sediments that separate two cratonic blocks, the Gawler Craton to the west and the Curnamona Province in the east. Previous studies of Helium isotopes in springs to the north of the area provide evidence of mantle-derived fluids that may influence faulting at depth. Our focal mechanism and stress inversion results show a regionally compressive stress field that provides no evidence for stress concentration. We also argue that mechanisms for localized faulting such as thermal weakening and isostatic rebound also fail to account for the occurrence of earthquakes at mid- to lower crustal depth in this area of high heat flow and that the focused seismicity can only be explained by high pore fluid pressure in the lower crust