Lankesteriana International Journal on Orchidology, Aug 30, 2016
Tropical Latin America is a nexus of tectonic plates whose relative motions have led to rapid tec... more Tropical Latin America is a nexus of tectonic plates whose relative motions have led to rapid tectonic and volcanic mountain building in late Neogene time. Tropical mountain building, in turn, leads to highland "cloud forest" microclimates with increased rainfall, lower diurnal temperatures, and diverse microclimates. I have previously emphasized how the geologically recent growth of mountains has been localized in Central America and that this is likely a factor in the high diversity and endemism in those highlands. This paper will show that Andean uplift accelerated at ~15 Ma ago and ~5 Ma BP and continues to this day. This process evolved geographically among the cordilleras of the region. Givnish and others recently presented phylogenomic evidence that the diversity of many epiphytic orchids, including tribes found in the neotropics, also accelerated during this time interval. Phylogenetic investigations of tropical orchid pollinators have shown that acceleration in speciation in such pollinators as hummingbirds, orchid bees, and flies occurred over this same time frame, suggesting that geologically driven environmental changes may have acted in concert with changes in orchid biology to speed up orchid diversity in these highlands. I also review some of the long-distance dispersal processes of orchids in the tropical Americas. River systems draining the Colombian Andes discharge into the Caribbean Sea and current-driven log-raft drifts and air suspension during cyclonic storms transport plants and animals from east to the west. Lastly I emphasize the need for the more information on orchid floras and species distribution in this hotspot.
The nearly continuous recovery of 0.5 km of generally fresh, layer 3 gabbroic rocks at Hole 735B,... more The nearly continuous recovery of 0.5 km of generally fresh, layer 3 gabbroic rocks at Hole 735B, especially near the bottom of the section, presents scientists an unusual opportunity to study the detailed elastic properties of the lower oceanic crust. Extending compressional-wave and density shipboard measurements at room pressure, V p and V s were measured at pressures from 20 to 200 MPa using the pulse transmission method. All of the rocks exhibit significant increases in velocity with increasing pressure up to about 150 MPa, a feature attributed to the closing of microcrack porosity. Measured velocities reflect the mineralogical makeup and microstructures acquired during the tectonic history of Hole 735B. Most of the undeformed and unaltered gabbros are approximately 65:35 plagioclase/ clinopyroxene rocks plus olivine or oxide minerals, and the observed densities and velocities are fully consistent with the Voigt-Reuss-Hill (VRH) averages of the component minerals and their proportions. Depending on their olivine content, the predominant olivine gabbros at 200 MPa have average V p = 7.1 ± 0.2 km/s, V s = 3.9 ± 0.1 km/s, and grain densities of 2.95 ± 0.5 g/cm 3 . The less abundant iron-titanium (Fe-Ti) oxide gabbros average V p = 6.75 ± 0.15 km/s, V s = 3.70 ± 0.1 km/s, and grain densities of 3.22 ± 0.05 g/cm 3 , reflecting the higher densities and lower velocities of oxide minerals compared to olivine. About 30% of the core is plastically deformed, and the densities and directionally averaged velocities of these shear-zone tectonites are generally consistent with those of the gabbros, their protoliths. Three sets of observations indicate that the shear-zone metagabbros are elastically anisotropic: (1) directional variations in V p , both vertical and horizontal and with respect to foliation and lineation; (2) discrepancies among V p values for the horizontal cores and the VRH averages of the component minerals and their mineral proportions, suggesting preferred crystallographic orientations of anisotropic minerals; and (3) variations of V s of up to 7%, with polarization directions parallel and perpendicular to foliation. Optical inspection of thin sections of the same samples indicates that plagioclase feldspar, clinopyroxene, and amphibole typically display crystallographic-preferred orientations, and this, plus the elastic anisotropy of these minerals, suggests that preferred orientations are responsible for much of the observed anisotropy, particularly at high pressure. Alteration tends to be localized to brittle faults and brecciated zones, and typical alteration minerals are amphibole and secondary plagioclase, which do not significantly change the velocity-density relationships.
What did happen can happen again [elsewhere]" -Paraphrased aphorism "Extreme events can and do ha... more What did happen can happen again [elsewhere]" -Paraphrased aphorism "Extreme events can and do happen…" -Thorne Lay and Hiroo Kanamori, Physics Today, 2011 "Hope for the best, but prepare for the worst." -An oft-quoted adage.
The SAFRR Tsunami Scenario was developed by a large team of experts from many different disciplin... more The SAFRR Tsunami Scenario was developed by a large team of experts from many different disciplines. The coordinating committee is the group who participated in the biweekly coordinating committee conference calls and assured that the different working groups communicated effectively.
Shorelines are highly variable environments characterized by a number of natural hazards, includi... more Shorelines are highly variable environments characterized by a number of natural hazards, including tsunami, storm surge, high winds, coastal erosion, sea-level rise, and high wave overtopping. Building on eroding coasts increases vulnerability to these hazards. Aerial view looking northwest of Makapuu Beach Park (foreground) and Waimanalo Bay in the distance, southeast Oahu, Hawai`i. Photograph by Bradley Romine, University of Hawai`i at Manoa.
It provided a view of the future, establishing science goals that reflected the USGS's fundamenta... more It provided a view of the future, establishing science goals that reflected the USGS's fundamental mission in areas of societal impact such as energy and minerals, climate and land use change, ecosystems, natural hazards, environmental health, and water. Intended to inform long-term program planning, the strategy emphasizes how USGS science can make substantial contributions to the well-being of the Nation and the world. In 2010, I realigned the USGS management and budget structure, changing it from a structure associated with scientific disciplines-Geography, Geology, Biology and Hydrology-to an issue-based organization along the lines of the Science Strategy. My aim was to align our management structure with our mission, our science priorities, our metrics for success, and our budget. An added benefit was that the USGS immediately appeared relevant to more Americans and it became easier for those outside the agency to navigate our organizational structure to find where within the USGS they would find the solution to their problem. External partners rarely approached us with a problem in "geology," but they might need help with an issue in climate change or energy research. The new organization is focused on seven science mission areas: The scope of each of these new mission areas is broader than the science directions outlined in the USGS Science Strategy and together cover the scope of USGS science activities. In 2010, I also commissioned seven Strategic Science Planning Teams (SSPTs) to draft science strategies for each USGS mission area. Although the existing Bureau Science Strategy could be a starting point for this exercise, the SSPTs had to go well beyond the scope of the existing document. What is of value and enduring from the work of the programs that existed under the former science disciplines needed to be reframed and reinterpreted under the new organization of the science mission areas. In addition, new opportunities for research directions have emerged in the five years since the Bureau Science Strategy was drafted, and exciting possibilities for cooperating and collaborating in new ways are enabled by the new mission focus of the organization. Scientists from across the Bureau were selected for these SSPTs for their experience in strategic planning, broad range of experience and expertise, and knowledge of stakeholder needs and relationships. Each SSPT was charged with developing a long-term (10-year) science strategy that encompasses the portfolio of USGS science in the respective mission area. Each science strategy will reinforce others because scientific knowledge inherently has significance to multiple issues. Leadership of the USGS and the Department of the Interior will use the science vision and priorities developed in these strategies for program guidance, implementation planning, accountability reporting, and resource allocation. These strategies will guide science and technology investment and workforce and human capital strategies. They will inform our partners regarding opportunities for communication, collaboration, and coordination. The USGS has taken a significant step toward demonstrating that we are ready to collaborate on the most pressing natural science issues of our day and the future. I believe a leadership aligned to support these issue-based science directions and equipped with the guidance provided in these new science strategies in the capable hands of our scientists will create a new era for USGS of which we can all be proud.
The radiated seismic energies (Es) of 980 shallow subduction-zone earthquakes with magnitudes > 5... more The radiated seismic energies (Es) of 980 shallow subduction-zone earthquakes with magnitudes > 5.8 are used to examine global patterns of energy release and apparent stress. In contrast to traditional methods which have relied upon empirical formulas, these energies are computed through direct spectral analysis of broadband seismic waveforms. Energy gives a physically different measure of earthquake size than moment. Moment, being derived from the low-frequency asymptote of the displacement spectra, is related to the final static displacement. Thus, moment is crucial to the long-term tectonic implication of an earthquake. In contrast, energy, being derived from the velocity power spectra, is more a measure of seismic potential for damage to anthropogenic structures. There is considerable scatter in the plot of Es-Mo for worldwide earthquakes. For any given MO, the ES can vary by as much as an order of magnitude about the mean regression line. The global variation between ES and M0, while large, is not random. When subsets of Es-Mo are plotted as a function of seismic region, tectonic setting and faulting type, the scatter in data is often substantially reduced. There are two profound implications for the estimation of seismic and tsunamic hazard. First, it is now feasible to characterize the apparent stress for particular regions. Second, a given MO does not have a unique ES. This means that MO alone is not sufficient to describe all aspects of an earthquake. In particular, we have found examples of interplate thrust-faulting earthquakes and intraslab normal-faulting earthquakes occurring in the same epicentral region with vastly different macroseismic effects. Despite the gross macroseismic disparities, the MW'S in these examples were identical. However, the Me's (energy magnitudes) successfully distinguished the earthquakes that were more damaging.
Cartography by James E. Queen, Will R. Stettner, and Paul Mathieux 1994 This map shows the Earth'... more Cartography by James E. Queen, Will R. Stettner, and Paul Mathieux 1994 This map shows the Earth's physiographic features, the current movements of its major tectonic plates, and the locations of its volcanoes, earthquakes, and impact craters. The use of color and shaded relief helps the reader to identify significant features of the land surface and the ocean floor. Over 1,500 volcanoes active during the past 10,000 years are plotted on the map in four age categories. The locations (epicenters) of over 24,000 earthquakes, largely from 1960 through 1990, are plotted in three magnitude categories and in two depth ranges. The map is intended as a teaching aid for classroom use and as a general reference for research. It is designed to show prominent global features when viewed from a distance and more detailed features upon closer inspection.
This contribution owes its origins to a paper and presentation by Dr. Calloway H. Dodson at the S... more This contribution owes its origins to a paper and presentation by Dr. Calloway H. Dodson at the Second International Conference on Neotropical Orchidology held in San José, Costa Rica in May of 2003 (Dodson 2003). Dr. Dodson outlined some of the reasons to suspect that regional geological fac- tors may play important roles in orchid speciation and biogeography and gave examples from the northwestern South America. He also suggested that evolutionary change in orchid might occur over fair- ly short time periods, perhaps even as short as decades, centuries or millennia (Dodson 2003, SHK lecture notes).
Desde hace muchos años, observaciones indican que sur-este de América Central es un punto de al... more Desde hace muchos años, observaciones indican que sur-este de América Central es un punto de alta diversidad de orquídeas. Éstas han sido confirmadas recientemente por estudios en la sistemática y listas anotadas este grupo. Un análisis de la distribución geográfica y altitudinal, demuestra que las especies más ampliamente distribuidas del “core” Maxillariinae se encuentran adaptadas para desarrollarse en tierras bajas cerca del nivel del mar, mientras que las especies endémicas y con distribuciones restringidas se encuentran en zonas altas y húmedas. Entre los recientes re-arreglos del “core” Maxillariinae, basado en filogenética molecular, aparece que el caldo Camaridium es el género más prominente en América Central, y está restringido a las tierras altas de Costa Rica y Panamá, indicando además que esta región es su lugar de origen y que sus límites para su dispersión son las tierras bajas y más secas. Las montañas de Costa Rica y Panamá se encuentran ent...
Using older and in part fl awed data, Ruff (1989) suggested that thick sediment entering the subd... more Using older and in part fl awed data, Ruff (1989) suggested that thick sediment entering the subduction zone (SZ) smooths and strengthens the trench-parallel distribution of interplate coupling. This circumstance was conjectured to favor rupture continuation and the generation of high-magnitude (≥Mw8.0) interplate thrust (IPT) earthquakes. Using larger and more accurate compilations of sediment thickness and instrumental (1899 to January 2013) and pre-instrumental era (1700-1898) IPTs (n = 176 and 12, respectively), we tested if a compelling relation existed between where IPT earthquakes ≥Mw7.5 occurred and where thick (≥1.0 km) versus thin (≤1.0 km) sedimentary sections entered the SZ. Based on the new compilations, a statistically supported statement (see Summary and Conclusions) can be made that high-magnitude earthquakes are most prone to nucleate at well-sedimented SZs. For example, despite the 7500 km shorter global length of thicksediment trenches, they account for ~53% of instrumental era IPTs ≥Mw8.0, ~75% ≥Mw8.5, and 100% ≥Mw9.1. No megathrusts >Mw9.0 ruptured at thin-sediment trenches, whereas three occurred at thick-sediment trenches (1960 Chile Mw9.5, 1964 Alaska Mw9.2, and 2004 Sumatra Mw9.2). However, large Mw8.0-9.0 IPTs commonly (n = 23) nucleated at thin-sediment trenches. These earthquakes are associated with the subduction of low-relief ocean fl oor and where the debris of subduction erosion thickens the plate-separating subduction channel. The combination of low bathymetric relief and subduction erosion is inferred to also produce a smooth trench-parallel distribution of coupling posited to favor the characteristic lengthy rupturing of highmagnitude IPT earthquakes. In these areas subduction of a weak sedimentary sequence further enables rupture continuation.
The U.S. Geological Survey and several partners operate a program called Science Application for ... more The U.S. Geological Survey and several partners operate a program called Science Application for Risk Reduction (SAFRR) that produces (among other things) emergency planning scenarios for natural disasters. The scenarios show how science can be used to enhance community resiliency. The SAFRR Tsunami Scenario describes potential impacts of a hypothetical but realistic tsunami affecting California (as well as the west coast of the United States, Alaska, and Hawaii) for the purpose of informing planning and mitigation decisions by a variety of stakeholders. The scenario begins with an Mw 9.1 earthquake off the Alaska Peninsula. With Pacific basin-wide modeling we estimate up to 5m waves and 10 m/sec currents would strike California 5 hours later. In marinas and harbors, 13,000 small boats are damaged or sunk (1 in 3) at a cost of $350 million, causing navigation and environmental problems. Damage in the Ports of Los Angeles and Long Beach amount to $110 million, half of it water damage to vehicles and containerized cargo. Flooding of coastal communities affects 1800 city blocks, resulting in $640 million in damage. The tsunami damages 12 bridge abutments and 16 lane-miles of coastal roadway, costing $85 million to repair. Fire and business interruption losses will substantially add to direct losses. Flooding affects 170,000 residents and workers. A wide range of environmental impacts could occur. An extensive public education and outreach program is underway, as well as an evaluation of the overall effort.
Journal of Geophysical Research: Solid Earth, 2010
Thousands of offshore repeating earthquakes with low‐angle thrust focal mechanisms occur along th... more Thousands of offshore repeating earthquakes with low‐angle thrust focal mechanisms occur along the subduction plate boundary of NE Japan. Double‐difference relocation methods using P‐ and S‐wave arrivals reveal clusters of events above these repeating events. To assure good depth control we restrict our study to events that are close to seismic stations. These “supraslab” earthquake clusters are regional features at depths of 25 to 50 km, and most of these clusters are below the depth of the forearc Moho, which we determined from converted waves. Seismicity over this depth range does not occur under the inland area of NE Japan except just below the vicinity of the arc volcanoes. Re‐entrants in the inner trench slope indicate that repeated collisions of seamounts have occurred in the past. Our preliminary interpretation of supraslab clusters is that they represent seismicity in seamounts detached from the Pacific plate during slab descent, driven by the resistance of seamounts to sub...
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