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Full-Text Articles in Physical Sciences and Mathematics
Seismic Slip Deficit In The Kashmir Himalaya From Gps Observations, Celia Schiffman, Bikram Singh Bali, Walter Szeliga, Roger Bilham
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 Mw = 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
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
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
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 …
A Catalog Of Felt Intensity Data For 570 Earthquakes In India From 1636 To 2009, Stacey Martin, Walter Szeliga
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
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
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 …
Seismic And Geodetic Constraints On Cascadia Slow Slip, Timothy I. Melbourne, Aaron G. Wech, Kenneth C. Creager
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
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. …
Gps Constraints On 34 Slow Slip Events Within The Cascadia Subduction Zone, 1997–2005, Walter Szeliga, Timothy I. Melbourne, Marcelo Santillan, Meghan Miller
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 …
Extent And Duration Of The 2003 Cascadia Slow Earthquake, Walter Szeliga, Timothy I. Melbourne, M. Meghan Miller, Victor Marcelo Santillan
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 …
Southern Cascadia Episodic Slow Earthquakes, Walter Szeliga, Timothy I. Melbourne, M. Meghan Miller, Marcelo Santillan
Southern Cascadia Episodic Slow Earthquakes, Walter Szeliga, Timothy I. Melbourne, M. Meghan Miller, Marcelo Santillan
Faculty Scholarship for the Cascadia Hazards Institute
Continuous GPS and seismic data from northern California show that slow earthquakes periodically rupture the Gorda-North America plate interface within southern Cascadia. On average, these creep events have occurred every 10.9±1.2 months since at least 1998. Appearing as week-long GPS extensional transients that reverse secular forearc contraction, the data show a recurrence interval 22% shorter than slow events recognized to the north. Seismic tremor here accompanies the GPS reversals, correlated across as many as 5 northern California seismometers. Tremor occurs sporadically throughout the year, but increases in duration and intensity by a factor of about 10 simultaneous with the GPS …
Precursory Transient Slip During The 2001 MW = 8.4 Peru Earthquake Sequence From Continuous Gps, Timothy I. Melbourne, Frank H. Webb
Precursory Transient Slip During The 2001 MW = 8.4 Peru Earthquake Sequence From Continuous Gps, Timothy I. Melbourne, Frank H. Webb
Faculty Scholarship for the Cascadia Hazards Institute
Two-hour position estimates from a continuous GPS station located at Arequipa, Peru, document precursory deformation beginning 18 hours prior to an Mw = 7.6 aftershock of the June 23rd 2001 Mw = 8.4 earthquake. This preseismic signal appears on the north and east components as a slow displacement with an amplitude twice that of the subsequent coseismic. Analysis of three years of 18-hour rate measurement shows this signal to be unprecedented and beyond four standard deviations from the mean rate. The best fitting centroid is directionally consistent with slow slip along the plate interface and suggests the preseismic …
Mantle Control Of Plate Boundary Deformation, Timothy I. Melbourne, Don Helmberger
Mantle Control Of Plate Boundary Deformation, Timothy I. Melbourne, Don Helmberger
Faculty Scholarship for the Cascadia Hazards Institute
The seismic wavefield propagating along the recently instrumented Pacific-North American plate boundary (California) displays remarkable variation, with regional shear waves arriving at coastal stations up to 20 seconds earlier than equidistant stations in eastern California. Broadband modeling of this data reveals that coastal paths sample fast upper mantle typical of Miocene-aged ocean plate (> 50 Km thickness). Inland paths sample slower uppermost mantle, with the seismic lithosphere, or lid, measuring less than 5 Km thick, characteristic of the Basin and Range extensional province. The boundary in the uppermost mantle between these provinces is sharp, expressing the juxtaposition of the stronger …
The Geodetic Signature Of The M8.0 Oct. 9, 1995, Jalisco Subduction Earthquake, Timothy I. Melbourne, I. Carmichael, C. Demets, K. Hudnut, O. Sanchez, J. Stock, G. Suarez, F. Webb
The Geodetic Signature Of The M8.0 Oct. 9, 1995, Jalisco Subduction Earthquake, Timothy I. Melbourne, I. Carmichael, C. Demets, K. Hudnut, O. Sanchez, J. Stock, G. Suarez, F. Webb
Faculty Scholarship for the Cascadia Hazards Institute
The October, 1995 Mw 8.0 Jalisco subduction earthquake has provided a thorough geodetic observation of the coseismic subduction process. An 11 station regional GPS network located directly onshore of the rupture demonstrates consistent vertical subsidence verified by tide gauge data and southwest-directed extension, with measured displacements reaching 1 meter. Unusually shallow and non-uniform faulting is required to explain the displacements. We determine that up to 5 meters of slip occurred within the upper 15 km of the thrust fault zone and 2 meters possibly as shallow as 8 km, and that slip was likely distributed in two main patches. The …