Near-field propagation of tsunamis from megathrust earthquakes

We investigate controls on tsunami generation and propagation in the near-field of great megathrust earthquakes using a series of numerical simulations of subduction and tsunamigenesis on the Sumatran forearc. The Sunda megathrust here is advanced in its seismic cycle and may be ready for another great earthquake. We calculate the seafloor displacements and tsunami wave heights for about 100 complex earthquake ruptures whose synthesis was informed by reference to geodetic and stress accumulation studies. Remarkably, results show that, for any near-field location: (1) the timing of tsunami inundation is independent of slip-distribution on the earthquake or even of its magnitude, and (2) the maximum wave height is directly proportional to the vertical coseismic displacement experienced at that location. Both observations are explained by the dominance of long wavelength crustal flexure in near-field tsunamigenesis. The results show, for the first time, that a single estimate of vertical coseismic displacement might provide a reliable short-term forecast of the maximum height of tsunami waves

The Ursinus Weekly, January 21, 1970

USGA plans to improve communications at Ursinus • Modified curriculum announced • Dr. Sachar discusses dissenters • Board of Directors increases tuition • Premed meeting • Free learning • Editorial: Tuition increase • Focus: Kim Brown • Faculty portrait: Dr. Conrad Kruse • Tiny time pills • Letters to the editor: Moratorium; Football congrats; Red neck • Administration answers • Sexton\u27s kind • Perspectives: On priorities • Ursinus pulverizes Diplomats by 76-56 for fifth triumph • Videon\u27s matmen fall to Albright • Final examination schedulehttps://digitalcommons.ursinus.edu/weekly/1154/thumbnail.jp

CANDELS: The Contribution of the Observed Galaxy Population to Cosmic Reionization

We present measurements of the specific ultraviolet luminosity density from a sample of 483 galaxies at 6<z<8. These galaxies were selected from new deep near-infrared HST imaging from the CANDELS, HUDF09 and ERS programs. In contrast to the majority of previous analyses, which assume that the distribution of galaxy ultraviolet (UV) luminosities follows a Schechter distribution, and that the distribution continues to luminosities far below our observable limit, we investigate the contribution to reionization from galaxies which we can observe, free from these assumptions. We find that the observable population of galaxies can sustain a fully reionized IGM at z=6, if the average ionizing photon escape fraction (f_esc) is ~30%. A number of previous studies have measured UV luminosity densities at these redshifts that vary by 5X, with many concluding that galaxies could not complete reionization by z=6 unless a large population of galaxies fainter than the detection limit were invoked, or extremely high values of f_esc were present. The observed UV luminosity density from our observed galaxy samples at z=7-8 is not sufficient to maintain a fully reionized IGM unless f_esc>50%. Combining our observations with constraints on the emission rate of ionizing photons from Ly-alpha forest observations at z=6, we can constrain f_esc<34% (2-sigma) if the observed galaxies are the only contributors to reionization, or <13% (2-sigma) if the luminosity function extends to M_UV = -13. These escape fractions are sufficient to complete reionization by z=6. These constraints imply that the volume ionized fraction of the IGM becomes less than unity at z>7, consistent with a number of complementary reionization probes. If faint galaxies dominate reionization, future JWST observations will probe deep enough to see them, providing an indirect constraint on the ionizing photon escape fraction [abridged].Comment: 16 pages, 7 figures, Submitted to the Astrophysical Journa

The Ursinus Weekly, February 20, 1970

Emig\u27s tenure ends; USGA holds election • President Helfferich retiring; Board of Directors outlines criteria for new President • Dean H. L. Jones hospitalized; recovering from heart attack • Festival of Arts to feature Sweet Stavin\u27 Chain, Smither • Editorial: Student power vacuum • Focus: Stu Sweet: Side one, side two • Faculty portrait: Eleanor Frost Snell • Immodest proposal • Absolute apathy • Administration answers: Financial aid • ProTheater on front stage • Perspectives: On Dick • Letters to the editor: Centennial issue; Bulletin • SFARC dissatisfied • Indoor trackmen compete during semester vacation • Bearettes initiate 5-girl basketball • Change of scenery • Badminton team starts with win • Bear hoopmen drop below .500 mark • Matmen lose by forfeits • Michener, Shepherd headline spring term Forum schedule • January graduates • Lorelei speakeasy • Chicago transit authority to perform at Albright • LIFE detects peace on college campushttps://digitalcommons.ursinus.edu/weekly/1155/thumbnail.jp

The Ursinus Weekly, April 17, 1970

Administration deals USGA policy slap • Earth Day planned April 22: Grass-roots pollution fight • 1970 UC Campus Chest attempts $3,000 goal • Youngbloods, MagMen appearing on April 23 • Editorial: Student Bill of Rights • Focus: Alice Johnson • Faculty portrait: Philip J. Rappoccio • Greener ginkgo trees • Contemplations: Bill of Rights • Committee report: UC Student Union • Chapter scholars named • From the other side: Heaven on earth? • Letters to the editor: Amico speaks; Arts Festival; Underground; Weekly; Student Union? • Bears battle Mules in season\u27s opener • Snell honored on May 22nd • Returning Bearettes bolster spring teams • U.C. netmen steal moral victory over Swarthmore • Bear trackmen whip everybody on cindershttps://digitalcommons.ursinus.edu/weekly/1158/thumbnail.jp

The Ursinus Weekly, March 6, 1970

Light show, Ben Hair Campus Chest events • USGA elects President: Novak, Emig meet press • Haas, Karpinski selected Woodrow Wilson scholars • Student Union to occupy Memorial Library building • Editorial: Student election, Ursinus style • Focus: John Fioravanti • Faculty self-portrait: Dr. Allan Lake Rice • Survey surveyed • Lantern in the limelight • Letters to the editor: Mr. Swarr; Dr. Helfferich; Sorority slander; Michener Forum • Perspectives: Drug forum • First semester Dean\u27s List • Kings and Queens crowned • Contemplations: Tom Rush • Matmen trim PMC for first win • Hoopmen sink Drexel • Badminton netgals prolong streak • Rams syndrome snaps Bearettes Boston-bound • 1970 Ursinus Festival of Artshttps://digitalcommons.ursinus.edu/weekly/1156/thumbnail.jp

The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity function at z=4-8. We use deep Hubble Space Telescope imaging over the CANDELS/GOODS fields, the Hubble Ultra Deep Field and the Year 1 Hubble Frontier Field deep parallel observations. These surveys provides an effective volume of 0.6-1.2 x 10^6 Mpc^3 over this epoch, allowing us to perform a robust search for faint (M_UV=-18) and bright (M_UV < -21) galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 galaxies at 3.51000 galaxies at z~6-8. We measure the luminosity function using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end our results agree with previous studies, yet we find a higher abundance of UV-bright galaxies at z>6, with M* ~ -21 at z>5, different than that inferred based on previous trends at lower redshift. At z=8, a single power-law provides an equally good fit to the UV luminosity function, while at z=6 and 7, an exponential cutoff at the bright-end is moderately preferred. We compare to semi-analytical models, and find that the lack of evolution in M* is consistent with models where the impact of dust attenuation on the bright-end of the luminosity function decreases at higher redshift. We measure the evolution of the cosmic star-formation rate density, correcting for dust attenuation, and find that it declines as (1+z)^(-4.3 +/- 0.5) at z>4, consistent with observations at z>9. Our observations are consistent with a reionization history that starts at z>10, completes at z>6, and reaches a midpoint (x_HII = 0.5) at 6.7<z<9.4. Finally, our observations predict that the abundance of bright z=9 galaxies is likely higher than previous constraints, though consistent with recent estimates of bright z~10 galaxies. [abridged]Comment: Re-submitted to the Astrophysical Journal after first referee's report. 34 pages, 21 figures, 7 tables. The source file includes a machine readable table of our full galaxy sampl