Rhett Butler - Academia.edu (original) (raw)

Papers by Rhett Butler

U.S. Government Printing Office eBooks, Mar 1, 1987

Geophysical Research Letters, 1996

Volcanic rocks collected on flowline traverses on the flanks of the East Pacific Rise (EPR) docum... more Volcanic rocks collected on flowline traverses on the flanks of the East Pacific Rise (EPR) document changes in axial magma chemistry with time, providing a record of the thermal history of axial magma chambers (AMC). We present data for a sample set of closely spaced (1-2 km) samples along EPR flowlines at three localities out to •-800 ka showing both steady (constant average temperature) and non-steady state behavior of magma chambers on time scales of 200-500 ka. Though based on only three symmetrical traverses so far, it appears that magmatically robust ridge locations (11 ø20'N and 9ø30'N) have steady state chambers, whereas a magmatically starved axis (10ø30'N) shows large temperature changes with time. These observations provide a new petrologic perspective to the ongoing debate regarding the significance and causes of morphologic variations along the axis of the East Pacific Rise.

short-period instruments arranged in a triangle around a broadband observatory-class three-compon... more short-period instruments arranged in a triangle around a broadband observatory-class three-component sensor. Sets of these small triads should be emplaced in larger triangular patterns, approximately 3500 km on a side, one each in the eastern and western hemispheres of Mars. Tentative locations for large triangle vertices consistent with the various scientific objectives include (l)west of Ascraeus Mons, north of eastern Valles Marineris, and in the southern highlands and (2) in the Elysium province, in the Isidis Basin, and in the northern lowlands.

Geophysical Journal International, 2020

Seismic attenuation is measured from a swarm of 50 earthquakes in Kīlauea volcano in 2018, associ... more Seismic attenuation is measured from a swarm of 50 earthquakes in Kīlauea volcano in 2018, associated with caldera collapse. The traverse extends at nearly constant azimuth to the saddle between Mauna Loa and Mauna Kea, continuing to Maui beneath the distal flanks of three dormant volcanos. From Maui the traverse then extends seaward to the Aloha Cabled Observatory (ACO) on the seafloor north of O‘ahu. The effective attenuation is measured with respect to an omega−2{\omega ^{ - 2}}omega−2 earthquake source model. Frequency dependent QP{Q_P}QP and QS{Q_S}QS are derived. The initial path is shallow and uphill, the path to Maui propagates at mid-crustal depths, and the path to ACO extends through oceanic crust. The observations of QPleQS{Q_P} \le {Q_S}QPleQS over each traverse are modelled as bulk attenuation QK{Q_K}QK. Several attenuation processes are observed, including Qmu{Q_\mu }Qmu, QK{Q_K}QK, QsimfQ\sim fQsimf, constant Q and scattering. The observation of bulk attenuation is ascribed to contrasting physical properties ...

Eos, Transactions American Geophysical Union, 2000

Frontiers in Marine Science, 2019

The ocean is key to understanding societal threats including climate change, sea level rise, ocea... more The ocean is key to understanding societal threats including climate change, sea level rise, ocean warming, tsunamis, and earthquakes. Because the ocean is difficult and costly to monitor, we lack fundamental data needed to adequately model, understand, and address these threats. One solution is to integrate sensors into future undersea telecommunications cables. This is the mission of the SMART subsea cables initiative (Science Monitoring And Reliable Telecommunications). SMART sensors would "piggyback" on the power and communications infrastructure of a million kilometers of undersea fiber optic cable and thousands of repeaters, creating the potential for seafloor-based global ocean observing at a modest incremental cost. Initial sensors would measure temperature, pressure, and seismic acceleration. The resulting data would address two critical scientific and societal issues: the longterm need for sustained climate-quality data from the under-sampled ocean (e.g., deep ocean temperature, sea level, and circulation), and the near-term need for improvements to global tsunami warning networks. A Joint Task Force (JTF) led by three UN agencies (ITU/WMO/UNESCO-IOC) is working to bring this initiative to fruition. This paper explores the ocean science and early warning improvements available

Geophysical Journal International

SUMMARYSeismic attenuation is measured from a swarm of 50 earthquakes in Kīlauea volcano in 2018,... more SUMMARYSeismic attenuation is measured from a swarm of 50 earthquakes in Kīlauea volcano in 2018, associated with caldera collapse. The traverse extends at nearly constant azimuth to the saddle between Mauna Loa and Mauna Kea, continuing to Maui beneath the distal flanks of three dormant volcanos. From Maui the traverse then extends seaward to the Aloha Cabled Observatory (ACO) on the seafloor north of O‘ahu. The effective attenuation is measured with respect to an omega−2{\omega ^{ - 2}}omega−2 earthquake source model. Frequency dependent QP{Q_P}QP and QS{Q_S}QS are derived. The initial path is shallow and uphill, the path to Maui propagates at mid-crustal depths, and the path to ACO extends through oceanic crust. The observations of QPleQS{Q_P} \le {Q_S}QPleQS over each traverse are modelled as bulk attenuation QK{Q_K}QK. Several attenuation processes are observed, including Qmu{Q_\mu }Qmu, QK{Q_K}QK, QsimfQ\sim fQsimf, constant Q and scattering. The observation of bulk attenuation is ascribed to contrasting physical prop...

Natural Hazards, 2016

The 2011 Tohoku earthquake and tsunami motivated an analysis of the potential for great tsunamis ... more The 2011 Tohoku earthquake and tsunami motivated an analysis of the potential for great tsunamis in Hawai'i that significantly exceed the historical record. The largest potential tsunamis that may impact the state from distant, Mw 9 earthquakes-as forecast by two independent tsunami models-originate in the Eastern Aleutian Islands. This analysis is the basis for creating an extreme tsunami evacuation zone, updating prior zones based only on historical tsunami inundation. We first validate the methodology by corroborating that the largest historical tsunami in 1946 is consistent with the seismologically determined earthquake source and observed historical tsunami amplitudes in Hawai'i. Using prior source characteristics of Mw 9 earthquakes (fault area, slip, and distribution), we analyze parametrically the range of Aleutian-Alaska earthquake sources that produce the most extreme tsunami events in Hawai'i. Key findings include: (1) An Mw 8.6 ± 0.1 1946 Aleutian earthquake source fits Hawai'i tsunami run-up/inundation observations, (2) for the 40 scenarios considered here, maximal tsunami inundations everywhere in the Hawaiian Islands cannot be generated by a single large earthquake, (3) depending on location, the largest inundations may occur for either earthquakes with the largest slip at the trench, or those with broad faulting over an extended area, (4) these extremes are shown to correlate with the frequency content (wavelength) of the tsunami, (5) highly variable slip along the fault strike has only a minor influence on inundation at these teletsunami distances, and (6) for a given maximum average fault slip, increasing the fault area does not generally produce greater run-up, as the additional wave energy enhances longer wavelengths, with a modest effect on inundation.

Physics of the Earth and Planetary Interiors, 2020

The Earth's Inner Core may rotate at a different speed than Earth's crust-mantle. We use observat... more The Earth's Inner Core may rotate at a different speed than Earth's crust-mantle. We use observations for antipodal earthquake and station pairs to examine the arrival time shift of the whispering-gallery wave which propagates tangentially along the top of the Inner Core. Observations of these waves for earthquakes which occurred at the same location reveal that travel times vary by ≥0.2 s over the past 20 years. We propose that these time shifts are caused by the interaction of a zero rigidity patch (lateral heterogeneity) at the Inner Core surface with the Inner Core differential rotation. The simplest interpretation infers a rotation rate of 0.05°/ year, which is one order of magnitude smaller than those reported by previous studies. Our result may also give constraint to the provenance of a zero rigidity patch at the Inner Core surface. The Fresnel zone coverage of whispering-gallery PKIIKP+… antipodal measurements beneath the Inner Core boundary extend over~60% of the boundary surface, in contrast to PKiKP-PKP paths which individually measure specular reflections (~1 Hz) from the top of the ICB over Fresnel zones each encompassing 0.002% of the Inner-Outer Core boundary.

Physics of the Earth and Planetary Interiors, 2021

Seismic evidence is presented for a high shear wave velocity, apparent discontinuity near ~100 km... more Seismic evidence is presented for a high shear wave velocity, apparent discontinuity near ~100 km depth within a portion of Earth's inner core. Antipodally (>179 •) focused data are stacked for five source-receiver diametric ray paths traversing the inner core. Two antipodal paths follow ray surfaces which are aligned with diameters between Tamanrasset (TAM), Algeria and Tonga earthquakes and Pitinga (PTGA), Brazil and Sulawesi earthquakes, providing clear examples of precursors to PKIIKP (an underside reflection at the inner core boundary). Waveform and stacked data (T > 4 s) were engaged in testing more than 16 inner core model series, varying compressional and shear wave velocities in upper inner core structures. The precursory seismic phases are successfully modeled as reflecting beneath a core liquid/solid interface at 100 km depth below the inner core boundary. This interface is highly reflective, and sensitive to a shear wave velocity contrast ≥5 km/s. An earlier precursory phase is observed at TAM and PTGA which may be modeled as an apparent discontinuity near ~250 km depth. This intermediate region has high shear wave velocities more akin to hcp-Fe mineralogy than Preliminary Reference Earth Model (PREM) values. Three other antipodal observations (China-Chile) nearly orthogonal to TAM paths exhibit seismic waves whose waveforms are more consistent with the PREM velocities above 100 km depth, while offering modest evidence for a solid/solid discontinuity at 100-km-depth. This research focused on seismology of the inner core potentially has mineral physics and geodynamic implications too broad to be simply encapsulated herein. Acknowledging some of these implications, we have focused upon measuring and mapping the seismic anomalies.

One of the primary objectives in placing seismic systems in deep-ocean boreholes is the detection... more One of the primary objectives in placing seismic systems in deep-ocean boreholes is the detection of teleseismic earthquakes and nuclear events. If the oceanic basement is substantially quieter than the ocean floor and island sites, then the added data could yield information of considerable value in nuclear test detection. This chapter presents and evaluates data relevant to this problem. The smallest teleseismic (Δ>30°) earthquake observed on the Hawaii Institute of Geophysics ocean sub-bottom seismometer (OSS) had a body-wave magnitude of 5.4. Only one nuclear explosion (mb = 5.6) was clearly observed. With additional filtering and processing, nuclear explosions as small as mb = 5.1 can be marginally observed. OSS records many regional earthquakes of the northwest circum-Pacific area that are not listed in the National Earthquake Information Service (NEIS) catalog. Teleseismic P-wave arrivals for several events contain frequencies as high as 8 Hz above the background noise. No...

Eos, 2004

This year, the Global Seismographic Network (GSN) surpassed its 128-station design goal for unifo... more This year, the Global Seismographic Network (GSN) surpassed its 128-station design goal for uniform worldwide coverage of the Earth.A total of 136 GSN stations are now sited from the South Pole to Siberia, and from the Amazon Basin to the sea floor of the northeast Pacific Ocean-in cooperation with over 100 host organizations and seismic networks in 59 countries worldwide (Figure 1). Established in 1986 by the Incorporated Research Institutions for Seismology (IRIS) to replace the obsolete, analog Worldwide Standardized Seismograph Network (WWSSN), the GSN continues a tradition in global seismology that dates back more than a century to the network of Milne seismographs that initially spanned the globe.The GSN is a permanent network of state-of-the-art seismological and geophysical sensors connected by available telecommunications to serve as a multi-use scientific facility and societal resource for scientific research, environmental monitoring, and education for our national and international community. All GSN data are freely and openly available via the Internet both in real-time and from archival storage at the IRIS Data Management System (www. iris.edu). GSN instrumentation is capable of measuring and recording with high fidelity all of Earth's vibrations, from high-frequency, strong ground motions near an earthquake, to the slowest free oscillations of the Earth (Figure 2). GSN seismometers have recorded both the greatest earthquakes on scale (for example, the 1994 Mw-8.2 Bolivia earthquake at 660 km depth; Wallace [1995]),as well as the nano-earthquakes (M < 0) near the sea floor at the Hawaii-2 Observatory [Butler, 2003]. GSN sensors are accurately calibrated, and timing is based on GPS clocks. The primary focus in creating the GSN has been seismology. However, the power, telemetry, site, and logistical infrastructure at GSN stations

Bulletin of the Seismological Society of America, 1994

Ambient seismic noise conditions at several sites on the Island of Hawaii have been studied by an... more Ambient seismic noise conditions at several sites on the Island of Hawaii have been studied by analyzing noise power spectral density (PSD) and signal-to-noise ratio (SNR) of teleseisms. Broadband digital waveform data used in this study were collected during Project ALOHA. Direct comparison of noise PSD and SNR of teleseisms simultaneously recorded at stations on Hawaii and at station KIP on Oahu indicates that the stations on Hawaii are quieter than station KIP on Oahu in the frequency band of 0.1 to 1 Hz, suggesting that the Island of Hawaii can provide better noise conditions than station KIP. Our interpretation of this observation is that the area and volume of Hawaii are much larger than those of Oahu and distances to the coast for the stations on Hawaii are larger than that for station KIP on Oahu. Stronger attenuation and relatively low coherency for teleseismic signals on Hawaii in frequencies of 0.4 to 1.2 Hz are attributed to the presence of partial melt in the upper mant...

Natural Hazards, 2017

We have reexamined the historical evidence in the circum-Pacific for the origin of the 1586 orpha... more We have reexamined the historical evidence in the circum-Pacific for the origin of the 1586 orphan tsunami of Sanriku, Japan, previously attributed to a Lima, Peru, earthquake and tsunami in 1586. New evidence comes from corals found in a unique paleotsunami deposit on Kaua'i. Dated by 230 Th-238 U geochronology these corals determine an absolute age in high precision of a Pacific tsunami event that was previously dated to approximately the sixteenth century by 14 C methodology. Detrital corrected ages of three low thorium, well-preserved coral clasts range from 415 to 464 years old (relative to 2016), with a mean age of 444 years ±21 (2r X). Literature evidence for circum-Pacific paleotsunami in this time range is reviewed in light of the new high-precision dating results. Modeled and observed tsunami wave amplitudes in Japan from several Peruvian events are insufficient to match the 1586 Sanriku observation, and paleodated earthquakes from Cascadia, the Alaskan Kodiak region, and Kamchatka are incompatible with the Sanriku data in several ways. However, a mega-earthquake (M w [ 9.25) in the Aleutians is consistent with the Kaua'i evidence, Pacific Northwest observations, and the Sanriku tsunami amplitude. The Kaua'i coral paleotsunami evidence therefore supports the origin of the 1586 Sanriku tsunami in the Aleutian Islands.

Seismological Research Letters, 2012

Physics of the Earth and Planetary Interiors, 1978

ABSTRACT

Geophysical Journal International, 1984

The variation of P-wave amplitudes between the eastern and western United States is examined by u... more The variation of P-wave amplitudes between the eastern and western United States is examined by using data from many different amplitude studies. Consideration is given to the geological siting of three groups of stations: (1) all stations, (2) stations situated on hard bedrock, and (3) all stations, but with sediment amplification corrections applied to stations situated on soft sediments. The average estimates of the three cases for the east versus west amplitude variation in the United States range from 0.12 to 0.21 magnitude units. The amplitude variation within the eastern, western and the United States as a whole is expressed in terms of the standard deviation of the station amplitude distribution. For the various regions and station groups studied, u ranges between 0.11 and 0.20 in magnitude units.

Seismological Society of America, Jun 1, 1980

Short-period P-wave amplitude data from nuclear explosions in the Soviet Union recorded by WWSSN ... more Short-period P-wave amplitude data from nuclear explosions in the Soviet Union recorded by WWSSN stations in the United States are presented. Thirtyfour events in five test sites are analyzed. The consistency and similarity of the initial P waveforms allow a stable amplitude measure. A well-defined amplitude pattern is obtained for each source region. The test sites at northern and southern Novaya Zemlya show a relative amplitude trend of a factor of 3 across the United States in their respective amplitude patterns. This is in contrast to two sites at Semipalatinsk which are in good relative agreement. A pattern of lateral variation of amplitude in the United States is obtained for a northern azimuth of approach. Stations situated on sediments are corrected for amplification effects. In contrast to previous studies, stations in the Western United States do not have systematically lower amplitudes than Eastern United States stations. Lowest amplitudes are found in Golden, Colorado (GOL) and Albuquerque, New Mexico (ALP), a factor of 4 lower than high amplitude stations. Preliminary amplitude data are presented from earthquakes in the Kuriles and South America. Events are chosen for consistency of waveforms across the United States to minimize earthquake source and directivity effects. These earthquake data indicate that amplitude variations in the United States are azimuthally dependent.

Seismological Society of America, Aug 1, 1980

Direct body waves and fundamental surface waves are calculated for a credible, hypothetical great... more Direct body waves and fundamental surface waves are calculated for a credible, hypothetical great earthquake on the San Andreas Fault. The prototype event assumed is the Fort Tejon earthquake of January 9, 1857. Amplitudes and durations of long-period ground motion (T > 1 sec) are found for a receiver in downtown Los Angeles. Calculations are carried out for various epicenters, dislocation profiles, and time functions. Ground motion from Love radiation is found to be most important, with peak-to-peak amplitudes up to 14 em and durations up to 5 min. This duration is a factor of 3 longer than has been assumed by previous design earthquakes whose estimates have been based upon acceleration criteria. Although the present result reveals several important features of long-period ground motion resulting from a great earthquake, more details of rupture propagation need to be known before a more definitive prediction can be made. The present result should be considered tentative.