The 4 April 2010 moment magnitude (M w) 7.2 El Mayor-Cucapah earthquake revealed the existence of a previously unidentifi ed fault system in Mexico that extends ~120 km from the northern tip of the Gulf of California to the U.S.-Mexico border. The system strikes northwest and is composed of at least seven major faults linked by numerous smaller faults, making this one of the most complex surface ruptures ever documented along the Pacifi c-North America plate boundary. Rupture propagated bilaterally through three distinct kinematic and geomorphic domains. Southeast of the epicenter, a broad region of distributed fracturing, liquefaction, and discontinuous fault rupture was controlled by a buried, southwest-dipping, dextral-normal fault system that extends ~53 km across the southern Colorado River delta. Northwest of the epicenter, the sense of vertical slip reverses as rupture propagated through multiple strands of an imbricate stack of eastdipping dextral-normal faults that extend ~55 km through the Sierra Cucapah. However, some coseismic slip (10-30 cm) was partitioned onto the west-dipping Laguna Salada fault, which extends parallel to the main rupture and defi nes the western margin of the Sierra Cucapah. In the northernmost domain, rupture terminates on a series of several north-northeast-striking cross-faults with minor offset (<8 cm) that cut uplifted and folded sediments of the northern Colorado River delta in the Yuha Desert. In the Sierra Cucapah, primary rupture occurred on four major faults separated by one fault branch and two accommodation zones. The accommodation zones are distributed in a left-stepping en echelon geometry, such that rupture passed systematically to structurally lower faults. The structurally lowest fault that ruptured in this event is inclined as shallowly as ~20°. Net surface offsets in the Sierra Cucapah average ~200 cm, with some reaching 300-400 cm, and rupture kinematics vary greatly along strike. Nonetheless, instantaneous extension directions are consistently oriented ~085° and the dominant slip direction is ~310°, which is slightly (~10°) more westerly than the expected azimuth of relative plate motion, but considerably more oblique to other nearby historical ruptures such as the 1992 Landers earthquake. Complex multifault ruptures are common in the central portion of the Pacifi c North American plate margin, which is affected by restraining bend tectonics, gravitational potential energy gradients, and the inherently three-dimensional strain of the transtensional and transpressional shear regimes that operate in this region.

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Infrared photometry and spectroscopy covering a time span of a quarter century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the -3exception of a major increase in emitted flux in a broad wavelength region centered near 3 µm in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 µm region throughout this span of time. In both stars the changes in the 1-5 µm flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly-simultaneous photometric data.

We present new observations of the far-ultraviolet (FUV; 1100-2200 ) radiation field and the near-to mid-A IR (3-13.5 mm) spectral energy distribution (SED) of a sample of T Tauri stars selected on the basis of bright molecular disks (GM Aur, DM Tau, and LkCa 15). In each source we find evidence for Lya-induced H 2 fluorescence and an additional source of FUV continuum emission below 1700 . Comparison of the FUV spectrå A to a model of H 2 excitation suggests that the strong continuum emission is due to electron impact excitation of H 2 . The ultimate source of this excitation is likely X-ray irradiation that creates hot photoelectrons mixed in the molecular layer. Analysis of the SED of each object finds the presence of inner disk gaps with sizes of a few AU in each of these young (∼1 Myr) stellar systems. We propose that the presence of strong H 2 continuum emission and inner disk clearing are related by the increased penetration power of high-energy photons in gasrich regions with low grain opacity.

Herbig Ae/Be stars are intermediate-mass pre-main sequence stars surrounded by circumstellar dust disks. Some are observed to produce jets, whose appearance as a sequence of shock fronts (knots) suggests a past episodic outflow variability. This "jet fossil record" can be used to reconstruct the outflow history. We present the first optical to near-infrared (NIR) spectra of the jet from the Herbig Ae star HD 163296, obtained with VLT/X-shooter. We determine the physical conditions in the knots and also their kinematic "launch epochs". Knots are formed simultaneously on either side of the disk, with a regular interval of ∼16 yr. The velocity dispersion versus jet velocity and the energy input are comparable between both lobes. However, the mass-loss rate, velocity, and shock conditions are asymmetric. We findṀ jet /Ṁ acc ∼ 0.01−0.1, which is consistent with magneto-centrifugal jet launching models. No evidence of any dust is found in the high-velocity jet, suggesting a launch region within the sublimation radius (<0.5 au). The jet inclination measured from proper motions and radial velocities confirms that it is perpendicular to the disk. A tentative relation is found between the structure of the jet and the photometric variability of the central source. Episodes of NIR brightening were previously detected and attributed to a dusty disk wind. We report for the first time significant optical fadings lasting from a few days up to a year, coinciding with the NIR brightenings. These are very likely caused by dust lifted high above the disk plane, and this supports the disk wind scenario. The disk wind is launched at a larger radius than the high-velocity atomic jet, although their outflow variability may have a common origin. No significant relation between outflow and accretion variability could be established. Our findings confirm that this source undergoes periodic ejection events, which may be coupled with dust ejections above the disk plane.

On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.

SAO 206462 (HD 135344B) has previously been identified as a Herbig F star with a circumstellar disk with a dip in its infrared excess near 10 μm. In combination with a low accretion rate estimated from Br γ , it may represent a gapped, but otherwise primordial or "pre-transitional" disk. We test this hypothesis with Hubble Space Telescope coronagraphic imagery, FUV spectroscopy and imagery and archival X-ray data, and spectral energy distribution (SED) modeling constrained by the observed system inclination, disk outer radius, and outer disk radial surface brightness (SB) profile using the Whitney Monte Carlo Radiative Transfer Code. The essentially face-on (i 20 •) disk is detected in scattered light from 0. 4 to 1. 15 (56-160 AU), with a steep (r −9.6) radial SB profile from 0. 6 to 0. 93. Fitting the SB data requires a concave upward or anti-flared outer disk, indicating substantial dust grain growth and settling by 8 ± 4 Myr. The warm dust component is significantly variable in near to mid-IR excess and in temperature. At its warmest, it appears confined to a narrow belt from 0.08 to 0.2 AU. The steep SED for this dust component is consistent with grains with a 2.5 μm. For cosmic carbon to silicate dust composition, conspicuous 10 μm silicate emission would be expected and is not observed. This may indicate an elevated carbon to silicate ratio for the warm dust, which is not required to fit the outer disk. At its coolest, the warm dust can be fit with a disk from 0.14 to 0.31 AU, but with a higher inclination than either the outer disk or the gaseous disk, providing confirmation of the high inclination inferred from mid-IR interferometry. In tandem, the compositional and inclination difference between the warm dust and the outer dust disk suggests that the warm dust may be of second-generation origin, rather than a remnant of a primordial disk component. With its near face-on inclination, SAO 206462's disk is a prime location for planet searches.

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