Physical Sciences and Mathematics Commons^™

Earthquakes, John J. Renton, Thomas Repine

Readings and Notes

For centuries, earth scientists have known where the major earthquakes occurred. They also knew they occurred in the same locales as the most violent volcanoes, a fact that led to centuries of arguments as to which was the cause of the other. Now we know that they are not cause and effect; they are both associated with the convergent plate margins. During the mid-1900s, another major zone of both volcanic and earthquake activity was discovered, namely the divergent margins, the most important site being the oceanic ridges. Since then, we have also come to understand the occurrence of volcanic activity …

Slip Pulse And Resonance Of The Kathmandu Basin During The 2015 Gorkha Earthquake, Nepal, John Galetzka, Walter Szeliga

All Faculty Scholarship for the College of the Sciences

Detailed geodetic imaging of earthquake ruptures enhances our understanding of earthquake physics and associated ground shaking. The 25 April 2015 moment magnitude 7.8 earthquake in Gorkha, Nepal was the first large continental megathrust rupture to have occurred beneath a high-rate (5-hertz) Global Positioning System (GPS) network. We used GPS and interferometric synthetic aperture radar data to model the earthquake rupture as a slip pulse ~20 kilometers in width, ~6 seconds in duration, and with a peak sliding velocity of 1.1 meters per second, which propagated toward the Kathmandu basin at ~3.3 kilometers per second over ~140 kilometers. The smooth slip …

Seismic-Hazard Map Of Southeast Missouri And Likely Magnitude Of The February 1812 New Madrid Earthquake, Jaewon Chung, J. David Rogers

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The New Madrid seismic zone lies beneath the upper Mississippi Embayment, straddling the border between southeastern Missouri and northwestern Tennessee. In late 1811 and early 1812, it produced five earthquakes of magnitudes >6.5, violently shaking the central and eastern United States (CEUS). Its magnitude and recurrence are of concern to today's central United States regions. By considering the effects of local geology, deterministic scenario maps (M_w 7.3 and 7.7) were produced for ground motions intended to simulate the 7 February 1812 event (NM3), which was the largest felt. These maps include spatial estimates of peak ground acceleration and of …

No Thermal Anomalies In The Mantle Transition Zone Beneath An Incipient Continental Rift: Evidence From The First Receiver Function Study Across The Okavango Rift Zone, Botswana, Youqiang Yu, Kelly H. Liu, M. Moidaki, Cory A. Reed, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Mechanisms leading to the initiation and early-stage development of continental rifts remain enigmatic, in spite of numerous studies. Among the various rifting models, which were developed mostly based on studies of mature rifts, far-field stresses originating from plate interactions (passive rifting) and nearby active mantle upwelling (active rifting) are commonly used to explain rift dynamics. Situated atop of the hypothesized African Superplume, the incipient Okavango Rift Zone (ORZ) of northern Botswana is ideal to investigate the role of mantle plumes in rift initiation and development, as well as the interaction between the upper and lower mantle. The ORZ developed within …

Azimuthal Anisotropy Beneath North Central Africa From Shear Wave Splitting Analyses, Awad A. Lemnifi, Kelly H. Liu, Stephen S. Gao, Cory A. Reed, Ahmed A. Elsheikh, Youqiang Yu, Abdala A. Elmelade

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

This study represents the first multistation investigation of azimuthal anisotropy beneath the interior of north central Africa, including Libya and adjacent regions, using shear wave splitting (SWS) analysis. Data used in the study include recently available broadband seismic data obtained from 15 stations managed by the Libyan Center for Remote Sensing and Space Science, and those from five other stations at which data are publicly accessible. A total of 583 pairs of high-quality SWS measurements utilizing the PKS, SKKS, and SKS phases demonstrate primarily N-S fast orientations with an average splitting delay time of approximately 1.2 s. An absence of …

The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence For Hydration And Thermal Upwellings, E. L. Emry, A. A. Nyblade, J. Juliá, S. Anandakrishnan, R. C. Aster, D. A. Wiens, Audrey D. Huerta, T. J. Wilson

All Faculty Scholarship for the College of the Sciences

Although prior work suggests that a mantle plume is associated with Cenozoic rifting and volcanism in West Antarctica, the existence of a plume remains conjectural. Here we use P wave receiver functions (PRFs) from the Antarctic POLENET array to estimate mantle transition zone thickness, which is sensitive to temperature perturbations, throughout previously unstudied parts of West Antarctica. We obtain over 8000 high‐quality PRFs using an iterative, time domain deconvolution method filtered with a Gaussian width of 0.5 and 1.0, corresponding to frequencies less than ∼0.24 and ∼0.48 Hz, respectively. Single‐station and common conversion point stacks, migrated to depth using the …

Dynamic Triggering In The Coso Geothermal Field, 2004-2013, Richard A. Alfaro-Diaz

Open Access Theses & Dissertations

We take advantage of EarthScope’s USArray Transportable Array (TA), regional seismic networks to investigate 154 M ≥ 7 earthquakes over a ten-year period (2004- 2013), in search of remotely triggered seismicity within the continental United States. We conduct an automated search to detect high frequency signals (which may indicate triggering of small local earthquakes) using a time window of 5 hours before and after each mainshock. The automated detection applies a short-term average (STA) to long-term-average (LTA) algorithms, to create a catalogue of detections. Using the catalog we search for an increase in detection rates after each main-shock. Sharp increases …

Mantle Transition Zone Discontinuities Beneath The Contiguous United States, Stephen S. Gao, Kelly H. Liu

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Using over 310,000 high-quality radial receiver functions recorded by the USArray and other seismic stations in the contiguous United States, the depths of the 410 km and 660 km discontinuities (d410 and d660) are mapped in over 1,000 consecutive overlapping circles with a radius of 1⁰. The average mantle transition zone (MTZ) thickness for both the western and central/eastern U.S. is within 3 km from the global average of 250 km, suggesting an overall normal MTZ temperature beneath both areas. The Pacific Coast Ranges and the southern Basin and Range Province are underlain by a depressed d410, indicating higher-than-normal temperature …

Seismic Imaging Of Mantle Transition Zone Discontinuities Beneath The Northern Red Sea And Adjacent Areas, A. A. Mohamed, Stephen S. Gao, A. A. Elsheikh, Kelly H. Liu, Youqiang Yu, R. E. Fat-Helbary

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

The dramatic asymmetry in terms of surface elevation, Cenozoic volcanisms and earthquake activity across the Red Sea is an enigmatic issue in global tectonics, partially due to the unavailability of broad-band seismic data on the African Plate adjacent to the Red Sea. Here, we report the first comprehensive image of the mantle transition zone (MTZ) discontinuities using data from the Egyptian National Seismic Network, and compare the resulting depths of the 410 and 660-km discontinuities with those observed on the Arabian side. Our results show that when a standard earth model is used for time-to-depth conversion, the resulting depth of …

A Uniform Database Of Teleseismic Shear Wave Splitting Measurements For The Western And Central United States, Kelly H. Liu, Ahmed Elsheikh, Awas Lemnifi, Uranbaigal Purevsuren, Melissa Ray, Hesham Refayee, Bin B. Yang, Youqiang Yu, Stephen S. Gao

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

We present a shear wave splitting (SWS) database for the western and central United States as part of a lasting effort to build a uniform SWS database for the entire North America. The SWS measurements were obtained by minimizing the energy on the transverse component of the PKS, SKKS, and SKS phases. Each of the individual measurements was visually checked to ensure quality. This version of the database contains 16,105 pairs of splitting parameters. The data used to generate the parameters were recorded by 1774 digital broadband seismic stations over the period of 1989-2012, and represented all the available data …

Doing More With Short Period Data: Determining Magnitudes From Clipped And Over-Run Seismic Data At Mount St. Helens, John J. Wellik Ii

Dissertations, Master's Theses and Master's Reports - Open

How can we calculate earthquake magnitudes when the signal is clipped and over-run? When a volcano is very active, the seismic record may saturate (i.e., the full amplitude of the signal is not recorded) or be over-run (i.e., the end of one event is covered by the start of a new event). The duration, and sometimes the amplitude, of an earthquake signal are necessary for determining event magnitudes; thus, it may be impossible to calculate earthquake magnitudes when a volcano is very active. This problem is most likely to occur at volcanoes with limited networks of short period seismometers. This …

The Crustal Thickness Of West Antarctica, Julien A. Chaput, Richard C. Aster, Audrey D. Huerta, X. Sun, Andrew Lloyd, Douglas A. Wiens, Andrew Nyblade, Sridhar Anandakrishnan, J. Paul Winberry, Terry Wilson

Geological Sciences Faculty Scholarship

P-to-S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica and the Transantarctic Mountains deployment of seismographic stations provide new estimates of crustal thickness across West Antarctica, including the West Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, and the Transantarctic Mountains (TAM) margin. We show that complications arising from ice sheet multiples can be effectively managed and further information concerning low-velocity subglacial sediment thickness may be determined, via top-down utilization of synthetic receiver function models. We combine shallow structure constraints with the response of deeper layers using a …

Seismic Slip Deficit In The Kashmir Himalaya From Gps Observations, Celia Schiffman, Bikram Singh Bali, Walter Szeliga, Roger Bilham

Faculty Scholarship for the Cascadia Hazards Institute

GPS measurements in Kashmir Himalaya reveal rangenormal convergence of 11±1 mm/yr with dextral shear of 5±1 mm/yr. The transition from a fully locked 170 km wide décollement to the unrestrained descending Indian plate occurs at ~25 km depth over an ~23 km wide transition zone. The convergence rate is consistent with the lower bounds of geological estimates for the Main Frontal Thrust, Riasi, and Balapora fault systems, on which no surface slip has been reported in the past millennium. Of the 14 damaging Kashmir earthquakes since 1123, none may have exceeded M_w = 7.6. Therefore, either a seismic moment …

Evolution Of Dike Opening During The March 2011 Kamoamoa Fissure Eruption, Kīlauea Volcano, Hawai'i, Paul Lundgren, Michael Poland, Asta Miklius, Tim Orr, Sang-Ho Yun, Eric Fielding, Zhen Liu, Scott Hensley, Susan Owen, Akiko Tanaka, Walter Szeliga

Faculty Scholarship for the Cascadia Hazards Institute

The 5–9 March 2011 Kamoamoa fissure eruption along the east rift zone of Kīlauea Volcano, Hawai`i, followed months of pronounced inflation at Kīlauea summit. We examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar (InSAR) data set in combination with continuous GPS data. We solve for distributed dike displacements using a whole Kīlauea model with dilating rift zones and possibly a deep décollement. Modeled surface dike opening increased from nearly 1.5 m to over 2.8 m from the first day to the end of the eruption, in agreement with field observations of surface fracturing. …

Gps Constraints On Indo-Asian Convergence In The Bhutan Himalaya: Segmentation And Potential For A 8.2-8.8 Mw Earthquake, Dowchu Drukpa, Phuntsho Pelgay, Anjan Bhattacharya, Phillipe Vernant, Walter Szeliga, Roser Bilham

Faculty Scholarship for the Cascadia Hazards Institute

The seismogenic setting of Bhutan is unusual due to its lower-than-average 20th century seismic moment release (Drukpa et al. 2006), its absence of a reliable historical record, and its unusual location near the Shillong plateau where a great earthquake in 1897 resulted in ≈10 m of N/S shortening of the Indian plate to its south (Gahalaut et al. 2011). Despite these indicators that lower than normal convergence velocities should currently prevail, the GPS velocity between Shillong and Lhasa suggests that convergence in Sikkim and Bhutan occurs at velocities exceeding 20 mm/yr. GPS points between the Greater Himalaya and the Shillong …

Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi

All Faculty Scholarship for the College of the Sciences

Despite an overall sinistral slip rate of ≈3 cm/yr, few major earthquakes have occurred in the past 200 years along the Chaman fault system, the western boundary of the India Plate with the Eurasia Plate. GPS and InSAR data reported here indicate sinistral shear velocities of 8–17 mm/yr across the westernmost branches of the fault system, suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east. At its southernmost on‐land segment (≈26°N), near the triple junction between the Arabia, Eurasia, and India Plates, we find the velocity across the …

Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi

Faculty Scholarship for the Cascadia Hazards Institute

Despite an overall sinistral slip rate of approximately 3 cm/yr, few major earthquakes have occurred in the past 200 years along the Chaman fault system, the western boundary of the India Plate with the Eurasia Plate. GPS and InSAR data reported here indicate sinistral shear velocities of 8-17 mm/yr across the westernmost branches of the fault system, suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east. At its southernmost on-land segment, near the triple junction between the Arabia, Eurasia, and India Plates, we find the velocity across the …

Effects Of High-Impedance-Contrast Boundary Upon Multi-Modal Seismic Surface Wave Data, Prajwol Tamrakar

UNLV Theses, Dissertations, Professional Papers, and Capstones

Synthetic studies and analyses of an experimental dataset were conducted to address the use of Rayleigh-type surface waves for estimation of shear wave velocity (VS) profiles of shallow bedrock sites. The shallow bedrock presents a high impedance contrast boundary which causes surface wave energy to be partitioned to higher modes. Idealized studies of hypothetical datasets and root-mean-squared calculations of error surfaces showed that if reliable dispersion data are available over a broad frequency spectrum, the VS profile can be recovered using the fundamental mode alone. However, when dispersion data are limited to a relatively narrow frequency band representing what might …

Crustal Structure And Evolution Beneath The Colorado Plateau And The Southern Basin And Range Province: Results From Receiver Function And Gravity Studies, Lamuail Bashir, Stephen S. Gao, Kelly H. Liu, Kevin Lee Mickus

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Over the past several decades, contrasting models have been proposed for the physical and chemical processes responsible for the uplift and long-term stability of the Colorado Plateau (CP) and crustal thinning beneath the Basin and Range Province (BRP) in the southwestern United States. Here we provide new constraints on the models by modeling gravity anomalies and by systematically analyzing over 15,500 P-to-S receiver functions recorded at 72 USArray and other broadband seismic stations on the southwestern CP and the southern BRP. Our results reveal that the BRP is characterized by a thin crust (28.2 ± 0.5 km), a mean V …

Geophysics At The Interface: Response Of Geophysical Properties To Solid-Fluid, Fluid-Fluid, And Solid-Solid Interfaces, Rosemary Knight, Laura J. Pyrak-Nolte, Lee D. Slater, Estella A. Atekwana, Anthony L. Endres, Jil T. Geller, David P. Lesmes, Seiji Nakagawa, Andre Revil, Mukul M. Sharma, Christian Straley

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Laboratory studies reveal the sensitivity of measured geophysical properties to solid-fluid, fluid-fluid, and solid-solid interfaces in granular and fractured materials. In granular materials, electrical properties and nuclear magnetic resonance relaxation times exhibit a strong dependence on the size and properties of the solid-fluid interface. The electrical and seismic properties of granular materials and the seismic properties of fractured materials reveal a dependence on the size or geometry of fluid-fluid interfaces. Seismic properties of granular and fractured materials are affected by the effective stress and cementing material at solid-solid interfaces. There have been some recent studies demonstrating the use of field-scale …

A Catalog Of Felt Intensity Data For 570 Earthquakes In India From 1636 To 2009, Stacey Martin, Walter Szeliga

Faculty Scholarship for the Cascadia Hazards Institute

Eight thousand three hundred thirty-nine intensity observations have been evaluated for earthquakes that occurred on the Indian subcontinent and surrounding plate boundaries from the seventeenth century to the present. They characterize 570 earthquakes, more than 90% of which occurred in the past two centuries. The electronic supplement to this article lists these data using European Macroseismic Scale (EMS-98) intensities with their geographic coordinates. We summarize these data graphically in the form of a spatially averaged intensity map for the subcontinent, a map that emphasizes the features of many previously published earthquake hazard maps for the Indian plate, but which more …

Intensity, Magnitude, Location, And Attenuation In India For Felt Earthquakes Since 1762, Walter Szeliga, Susan Hough, Stacey Martin, Roger Bilham

Faculty Scholarship for the Cascadia Hazards Institute

A comprehensive, consistently interpreted new catalog of felt intensities for India (Martin and Szeliga, 2010, this issue) includes intensities for 570 earthquakes; instrumental magnitudes and locations are available for 100 of these events. We use the intensity values for 29 of the instrumentally recorded events to develop new intensity versus attenuation relations for the Indian subcontinent and the Himalayan region. We then use these relations to determine the locations and magnitudes of 234 historical events, using the method of Bakun and Wentworth (1997). For the remaining 336 events, intensity distributions are too sparse to determine magnitude or location. We evaluate …

Future Cascadia Megathrust Rupture Delineated By Episodic Tremor And Slip, James S. Chapman, Timothy I. Melbourne

Faculty Scholarship for the Cascadia Hazards Institute

A suite of 15 episodic tremor and slip events imaged between 1997 and 2008 along the northern Cascadia subduction zone suggests future coseismic rupture will extend to 25 km depth, or approximately 60 km inland of the Pacific coast, rather than stopping offshore at 15 km depth. An ETS-derived coupling profile accurately predicts GPS measured interseismic deformation of the overlying North American plate, as measured by approximately 50 continuous GPS stations across western Washington State. When extrapolated over the 550-year average recurrence interval of Cascadia megathrust events, the coupling model also replicates the pattern and amplitude of coseismic coastal subsidence …

Microbial-Induced Heterogeneity In The Acoustic Properties Of Porous Media, Caroline A. Davis, Laura J. Pyrak-Nolte, Estella A. Atekwana, D. Dale, Werkema, Marisa E. Haugen

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

It is not known how biofilms affect seismic wave propagation in porous media. Such knowledge is critical for assessing the utility of seismic techniques for imaging biofilm development and their effects in field settings. Acoustic wave data were acquired over a two-dimensional region of a microbial-stimulated sand column and an unstimulated sand column. The acoustic signals from the unstimulated column were relatively uniform over the 2D scan region. The data from the microbial-stimulated column exhibited a high degree of spatial heterogeneity in the acoustic wave amplitude, with some regions exhibiting significant increases in attenuation while others exhibited decreases. Environmental scanning …

Seismic And Geodetic Constraints On Cascadia Slow Slip, Timothy I. Melbourne, Aaron G. Wech, Kenneth C. Creager

Faculty Scholarship for the Cascadia Hazards Institute

Automatically detected and located tremor epicenters from episodic tremor and slip (ETS) episodes in northern Cascadia provide a high-resolution map of Washington’s slow slip region. Thousands of epicenters from the past four ETS events from 2004 to 2008 provide detailed map-view constraints that correlate with geodetic estimates of the simultaneous slow slip. Each of these ETS events exhibits remarkable similarity in the timing and geographic distribution of tremor density and geodetically inferred slip. Analysis of the latest 15-month inter-ETS period also reveals ageodetic tremor activity similar both in duration and extent to ETS tremor. Epicenters from both ETS and inter- …

Fold And Thrust Partitioning In A Contracting Fold Belt: Insights From The 1931 Mach Earthquake In Baluchistan, Walter Szeliga, Roger Bilham, Daniel Schelling, Din Mohamed Kakar, Sarosh Lodi

Faculty Scholarship for the Cascadia Hazards Institute

Surface deformation associated with the 27 August 1931 earthquake near Mach in Baluchistan is quantified from spirit-leveling data and from detailed structural sections of the region interpreted from seismic reflection data constrained by numerous well logs. Mean slip on the west dipping Dezghat/Bannh fault system amounted to 1.2 m on a 42 km x 72 km thrust plane with slip locally attaining 3.2 m up dip of an inferred locking line at approximately 9 km depth. Slip also occurred at depths below the interseismic locking line. In contrast, negligible slip occurred in the 4 km near the interseismic locking line. …

Characterizing The Deformation Of Reservoirs Using Interferometry, Gravity, And Seismic Analyses, Cara Schiek

Open Access Theses & Dissertations

In this Dissertation, I characterize how reservoirs deform using surface and subsurface techniques. The surface technique I employ is radar interferometry, also known as InSAR (Interferometric Synthetic Aperture Radar). The subsurface analyses I explore include gravity modeling and seismic techniques consisting of determining earthquake locations from a small-temporary seismic network of six seismometers. These techniques were used in two different projects to determine how reservoirs deform in the subsurface and how this deformation relates to its remotely sensed surface deformation.

The first project uses InSAR to determine land subsidence in the Mimbres basin near Deming, NM. The land subsidence measurements …

Gps Constraints On 34 Slow Slip Events Within The Cascadia Subduction Zone, 1997–2005, Walter Szeliga, Timothy I. Melbourne, Marcelo Santillan, Meghan Miller

Faculty Scholarship for the Cascadia Hazards Institute

Refinements to GPS analyses in which we factor geodetic time series to better estimate both reference frames and transient deformation resolve 34 slow slip events located throughout the Cascadia subduction zone from 1997 through 2005. Timing of transient onset is determined with wavelet transformation of geodetic time series. Thirty continuous stations are included in this study, ranging from northern California to southwestern British Columbia. Our improvements in analysis better resolve the largest creep events and also identify many smaller events. At 48.5 degrees N latitude, a 14-month average recurrence interval has been observed over eight events since 1997. Farther north …

Active-Passive Array Surface Wave Inversion And Comparison To Borehole Logs In Southeast Missouri, Alexei A. Malovichko, Neil Lennart Anderson, Dmitriy A. Malovichko, Denis Yu Shylakov, Pavel G. Butirin

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

In May 2002, both active- and passive-source surface wave data were acquired using 4-channel arrays at six selected bridge sites in southeast Missouri. Processing of acquired data (increase of signal-to-noise ratio, estimation of phase velocities) was carried out and dispersion curves of Rayleigh wave phase velocities were constructed. Each fundamental mode dispersion curve was then inverted by linearised optimization to a layered shear-wave velocity profile to depths of up to 60 m. The estimated shear-wave velocity profiles were compared to other geotechnical data that had been previously acquired at each test site for the Missouri Department of Transportation (MoDOT) including …

Extent And Duration Of The 2003 Cascadia Slow Earthquake, Walter Szeliga, Timothy I. Melbourne, M. Meghan Miller, Victor Marcelo Santillan

Faculty Scholarship for the Cascadia Hazards Institute

Inversion of continuous GPS measurements from the Pacific Northwest show the 2003 Cascadia slow earthquake to be among the largest of ten transients recognized here. Twelve stations bracketing slow slip indicate transient slip propagated bi-directionally from initiation in the southern Puget basin, reaching 300 km along-strike over a period of seven weeks. This event produced, for the first time, resolvable vertical subsidence, and horizontal displacement reaching six mm in southern Washington State. Inverted for non-negative thrust slip, a maximum of 3.8 cm of slip is inferred, centered at 28 km depth near the sharp arch in the subducting Juan de …