Author
Mark Simons
Other affiliations: Massachusetts Institute of Technology
Bio: Mark Simons is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Interferometric synthetic aperture radar & Slip (materials science). The author has an hindex of 63, co-authored 176 publications receiving 11943 citations. Previous affiliations of Mark Simons include Massachusetts Institute of Technology.
Papers published on a yearly basis
Papers
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TL;DR: Detailed geophysical measurements reveal features of the 2011 Tohoku-Oki megathrust earthquake and suggest the need to consider the potential for a future large earthquake just south of this event.
Abstract: Geophysical observations from the 2011 moment magnitude (M_w) 9.0 Tohoku-Oki, Japan earthquake allow exploration of a rare large event along a subduction megathrust. Models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places.
Sources of high-frequency seismic waves delineate the edges of the
deepest portions of coseismic slip and do not simply correlate with the
locations of peak slip. Relative to the M_w 8.8 2010 Maule, Chile
earthquake, the Tohoku-Oki earthquake was deficient in high-frequency
seismic radiation-a difference that we attribute to its relatively
shallow depth. Estimates of total fault slip and surface secular strain
accumulation on millennial time scales suggest the need to consider the
potential for a future large earthquake just south of this event.
691 citations
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TL;DR: RO1_PAC as mentioned in this paper is a Repeat Orbit Interferometry package that allows topographic and surface change researchers to apply Interferometric Synthetic Aperture Radar (InSAR) methods.
Abstract: RO1_PAC V2.3, a Repeat Orbit Interferometry package that allows topographic and surface change researchers to apply Interferometric Synthetic Aperture Radar (InSAR) methods, is now freely available to the community InSAR is the synthesis of conventional SAR and interferometry techniques that have been developed over several decades in radio astronomy and radar remote sensing. In recent years, it has opened entirely new application areas for radar in the Earth system sciences, including topographic mapping and geodesy.
RO1_PAC, developed primarily to work with European Remote Sensing (ERS) satellite radar data, currently supports ERS-1, ERS-2, and Japanese Earth Resources Satellite (JERS) radar data, and is configurable to work with “strip-mode” data from all existing satellite radar instruments. The first release of RO1_ PAC (V1.0) was made quietly in 2000, and roughly 30 groups in the academic and research community currently use it.
623 citations
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TL;DR: It is observed that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution ofAftershocks is governed by afterslip.
Abstract: Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (M_w) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a M_w 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and the up-dip creeping zone. We observe that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution of aftershocks is governed by afterslip.
487 citations
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TL;DR: In this paper, the authors used InSAR data to derive continuous maps for three orthogonal components of the co-seismic surface displacement field due to the 1999 M_w7.1 Hector Mine earthquake in southern California.
Abstract: We use Interferometric Synthetic Aperture Radar (InSAR) data to derive continuous maps for three orthogonal components of the co-seismic surface displacement field due to the 1999 M_w7.1 Hector Mine earthquake in southern California. Vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane, consistent with predictions of linear elastic models of deformation for a strike-slip fault. Some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry.
452 citations
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TL;DR: The InSAR-derived surface displacement data from the Bam and other large shallow earthquakes suggest that the uppermost section of the seismogenic crust around young and developing faults may undergo a distributed failure in the interseismic period, thereby accumulating little elastic strain.
Abstract: Our understanding of the earthquake process requires detailed insights into how the tectonic stresses are accumulated and released on seismogenic faults. We derive the full vector displacement field due to the Bam, Iran, earthquake of moment magnitude 6.5 using radar data from the Envisat satellite of the European Space Agency. Analysis of surface deformation indicates that most of the seismic moment release along the 20-km-long strike-slip rupture occurred at a shallow depth of 4‐5km, yet the rupture did not break the surface. The Bam event may therefore represent an endmember case of the ‘shallow slip deficit’ model, which postulates that coseismic slip in the uppermost crust is systematically less than that at seismogenic depths (4‐10km). The InSAR-derived surface displacement data from the Bam and other large shallow earthquakes suggest that the uppermost section of the seismogenic crust around young and developing faults may undergo a distributed failure in the interseismic period, thereby accumulating little elastic strain.
439 citations
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TL;DR: Long-term sea level peaked at 100 ± 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred, and presents a new sea-level record for the past 100 million years.
Abstract: We review Phanerozoic sea-level changes [543 million years ago (Ma) to the present] on various time scales and present a new sea-level record for the past 100 million years (My). Long-term sea level peaked at 100 ± 50 meters during the Cretaceous, implying that ocean-crust production rates were much lower than previously inferred. Sea level mirrors oxygen isotope variations, reflecting ice-volume change on the 10 4 - to 10 6 -year scale, but a link between oxygen isotope and sea level on the 10 7 -year scale must be due to temperature changes that we attribute to tectonically controlled carbon dioxide variations. Sea-level change has influenced phytoplankton evolution, ocean chemistry, and the loci of carbonate, organic carbon, and siliciclastic sediment burial. Over the past 100 My, sea-level changes reflect global climate evolution from a time of ephemeral Antarctic ice sheets (100 to 33 Ma), through a time of large ice sheets primarily in Antarctica (33 to 2.5 Ma), to a world with large Antarctic and large, variable Northern Hemisphere ice sheets (2.5 Ma to the present).
2,740 citations
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TL;DR: The Mars Orbiter Laser Altimeter (MOLA) has been used to measure the topography, surface roughness, and 1.064-μm reflectivity of Mars and the heights of volatile and dust clouds as mentioned in this paper.
Abstract: The Mars Orbiter Laser Altimeter (MOLA), an instrument on the Mars Global Surveyor spacecraft, has measured the topography, surface roughness, and 1.064-μm reflectivity of Mars and the heights of volatile and dust clouds. This paper discusses the function of the MOLA instrument and the acquisition, processing, and correction of observations to produce global data sets. The altimeter measurements have been converted to both gridded and spherical harmonic models for the topography and shape of Mars that have vertical and radial accuracies of ~1 m with respect to the planet's center of mass. The current global topographic grid has a resolution of 1/64° in latitude × 1/32° in longitude (1 × 2 km^2 at the equator). Reconstruction of the locations of incident laser pulses on the Martian surface appears to be at the 100-m spatial accuracy level and results in 2 orders of magnitude improvement in the global geodetic grid of Mars. Global maps of optical pulse width indicative of 100-m-scale surface roughness and 1.064-μm reflectivity with an accuracy of 5% have also been obtained.
1,542 citations
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TL;DR: Cessation of rapid Pacific trench migration coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern Tibet.
Abstract: The geological evolution of the Tibetan plateau is best viewed in a context broader than the India-Eurasia collision zone. After collision about 50 million years ago, crust was shortened in western and central Tibet, while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western Pacific and Indonesia. Cessation of rapid Pacific trench migration (∼15 to 20 million years ago) coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern Tibet. The latter appear to result from rapid eastward flow of the deep crust, probably within crustal channels imaged seismically beneath eastern Tibet. These events mark a transition to the modern structural system that currently accommodates deformation within Tibet.
1,292 citations
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TL;DR: In this paper, a new InSAR persistent scatterer (PS) method was proposed for analyzing episodic crustal deformation in non-urban environments, with application to volcanic settings.
Abstract: [1] We present here a new InSAR persistent scatterer (PS) method for analyzing episodic crustal deformation in non-urban environments, with application to volcanic settings. Our method for identifying PS pixels in a series of interferograms is based primarily on phase characteristics and finds low-amplitude pixels with phase stability that are not identified by the existing amplitude-based algorithm. Our method also uses the spatial correlation of the phases rather than a well-defined phase history so that we can observe temporally-variable processes, e.g., volcanic deformation. The algorithm involves removing the residual topographic component of flattened interferogram phase for each PS, then unwrapping the PS phases both spatially and temporally. Our method finds scatterers with stable phase characteristics independent of amplitudes associated with man-made objects, and is applicable to areas where conventional InSAR fails due to complete decorrelation of the majority of scatterers, yet a few stable scatterers are present.
1,242 citations
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TL;DR: The plutonic archive is unlocked through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia.
Abstract: Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.
1,086 citations