Intermediate-period Rayleigh and Love waves propagating across Tibet require marked radial anisotropy within the mid-lower crust, consistent with a thinning of it. The anisotropy is largest in the western part of the plateau where the moment tensors of earthquakes indicate active crustal thinning. A preferred orientation of mica crystals resulting from the crustal thinning can account for the o...

Four crustal xenoliths from Scotland have been dissected in order to evaluate the effects of magma-xenolith interaction on Rb-Sr and Sm-Nd isotopic systematics, and hence the use of the xenoliths for accurate determination of source compositions. Each xenolith was sampled from the edge to the center, The Nd isotopic compositions are virtually uniform across each xenolith; however, there are sig...

The Ontong Java, Manihiki, and Shatsky oceanic plateaus are among the Earth’s largest igneous provinces and are commonly believed to have erupted rapidly during the surfacing of giant heads of initiating mantle plumes. We investigate this hypothesis by using sediment descriptions of Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill cores to constrain plateau subsidence his...

The performance of off-policy learning, including deep Q-learning and deep deterministic policy gradient (DDPG), critically depends on the choice of the exploration policy. Existing exploration methods are mostly based on adding noise to the on-going actor policy and can only explore local regions close to what the actor policy dictates. In this work, we develop a simple meta-policy gradient al...

S U M M A R Y We compare 3-D upper mantle anisotropic structures beneath the North American continent obtained using standard and improved crustal corrections in the framework of Non-linear Asymptotic Coupling Theory (NACT) applied to long period three component fundamental and higher mode surface waveform data. Our improved approach to correct for crustal structure in high-resolution regional ...

[1] Surface wave dispersion measurements from ambient seismic noise and array‐based measurements from teleseismic earthquakes observed with the EarthScope/USArray Transportable Array (TA) are inverted using a Monte Carlo method for a 3‐D VS model of the crust and uppermost mantle beneath the western United States. The combination of data from these methods produces exceptionally broadband dispe...

We introduce topic exploration, a new approach to information discovery on the web that differs significantly from conventional web search. We then explain why the Deep Web, an inhospitable region for web crawlers, is emerging as a significant information resource. Finally, we describe the anatomy of Kosmix, the first general-purpose topic exploration engine to harness the Deep Web. The Kosmix ...

Evolution strategies (ES) are a family of blackbox optimization algorithms able to train deep neural networks roughly as well as Q-learning and policy gradient methods on challenging deep reinforcement learning (RL) problems, but are much faster (e.g. hours vs. days) because they parallelize better. However, many RL problems require directed exploration because they have reward functions that a...