The recently discovered γ-ray binary 1FGL J1018.6-5856 has a proposed optical/near-infrared (OIR) counterpart 2MASS 10185560-5856459. We present Strömgren photometry of this star to investigate its photometric variability and measure the reddening and distance to the system. We find that the γ-ray binary has E(B − V ) = 1.34 ± 0.04 and d = 5.4 +4.6 −2.1 kpc. . While E(B − V ) is consistent with X-ray observations of the neutral hydrogen column density, the distance is somewhat closer than some previous authors have suggested.

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Large magnitude offshore passive margin earthquakes are rare, making small magnitude events (M < 4) the predominant data available to study the mechanisms of seismicity along passive margins. This study is focused on a swarm of events (M2.1-M3.9) that occurred from 2012-2013 located in the Gulf of Maine (GM) along the Atlantic Passive Margin (APM) shelf break, a region with previously minimal recorded seismic activity. Relative locations were calculated for the earthquakes of the GM swarm and a moment tensor inversion method was used to calculate focal mechanisms for the two largest events in the swarm. The results of the relative location method constrained a fault orientation to a strike of 243° ± 3° and a dip of 25° ± 3°. The focal mechanisms for the two largest events were determined to be oblique normal faults with steeply dipping planes at depths between 12-18 km. For the largest event (M3.9), the strike is 235° ± 1°, with a dip of 77.7° ± .8° and a rake of-116.5° ± 3°, and for the second largest event (M3.7) the strike is 259° ± 3°, with a dip of 78° ± 2° and a rake of-58.8° ± 7°. By mapping the spatial extent of the relative hypocenters, I infer a potential fault size of 2.7 km by 2.4 km. If this entire area were to rupture at once in the future, an earthquake of M4.9-M5.0 could occur, a magnitude not large enough to be tsunamigenic in the GM. Based on Gutenberg-Richter relations from the eastern APM, if a M7 can occur in the GM, its estimated mean repeat time is 2,120-22,800 years, and it could be tsunamigenic depending on the event's proximity to the continental slope.

The traditional M s :m b discrimination method is routinely used for distinguishing between earthquakes and explosions within dense networks, but there is a need to improve discrimination at smaller magnitudes; therefore, we need magnitude scales that can successfully be applied to data from sparse networks. We developed a unified Rayleigh-and Love-wave magnitude scale (M s U) that is designed to maximize available information from single stations and then combine magnitude estimates into network averages. By combining Love-and Rayleigh-wave amplitudes, we minimize the effect of earthquake radiation patterns from sparse networks, thereby improving discrimination between earthquakes and explosions. M s U is built from M s V MAX (Russell, 2006) and is calculated from Love and Rayleigh waves that are narrowband filtered and corrected for propagation and source effects at periods between 8 and 25 s to find filter bands of maximum energy propagation. The data are also corrected for censoring effects at the station level, because either Rayleigh or Love waves may be below the signal-to-noise ratio threshold at a given period.We applied M s U to 39 earthquakes (3:21 < M w < 5:08) located in the Yellow Sea and Korean Peninsula region, as well as to the three North Korean nuclear tests (4:1 < m b < 5:1). By using M s U:m b as a discriminant, there is an increase in the separation of small magnitude earthquakes and explosions in sparse networks and a significant reduction in outliers, as shown in the application from the Korean Peninsula. This research addresses the theory, methods, and capability of M s U as a discriminant.