Seismic Assessments of the Hikurangi and Aleutian-Alaska Subduction Zones

Subduction zones around the world indicate remarkably diverse and complex systems. In this dissertation, I will focus on the seismic characteristics of two subduction zones: the Hikurangi Subduction Zone (HSZ) and the Aleutian-Alaska Subduction Zone (AASZ). For the HSZ, the goal is to derive the 3-D Vp model by taking advantage of the teletomoDD package (an iterative nested regional-global tomographic algorithm). For the &nbsp;AASZ, we use the available 3-D velocity model in the area. We aim to improve the absolute location of the earthquakes using the 3-D Vp models in these subduction zones. To enhance the relative locations, we take advantage of the differential-time relocation method based on waveform cross-correlation. Chapter 3 is focused on the HSZ. I describe our 3-D Vp model and relocation catalogs in this Chapter. I discuss an interesting correlation between Vp anomalies, seismicity distributions, and temperature models. I discuss the Taupo volcanic zone and its characteristics. I also look into the relationship between the result of this work and other data or models (e.g., slab interface models, geological terrane, coupling, and slow slip events). Chapter 4 is devoted to the AASZ. In this chapter, we focus on the distribution of the double seismic zones along the AASZ. We discuss the unique features observed for the AASZ using the waveform cross-correlation relocation results (e.g., Yakutat slab, Denali Gap, slow slip events).&nbsp;</p

Double seismic zones along the eastern Aleutian-Alaska subduction zone revealed by a high-precision earthquake relocation catalog

The Eastern Aleutian-Alaska Subduction Zone (EAASZ) manifests significant along-strike variations in structure and geometry. The limited spatial resolution in intermediate-depth earthquake locations precludes investigation of small-scale variations in seismic characteristics. In this study, we use an existing 3D seismic velocity model and waveform cross-correlation data to relocate the earthquakes in 2016 near the EAASZ. Our improved absolute and relative earthquake locations reveal complex spatial characteristics of double seismic zones (DSZs). There are significant variations in location, depth, layer separation, and length of the DSZs along the EAASZ. We also observe nonuniform layer separations along the slope of the subducting slab that may imply either rheological or crustal thickness variations. In addition, our results suggest a triple seismic zone (TSZ) beneath Kenai. The interplay among different factors, including dehydration of metamorphic facies, intraslab stress, preexisting structures, and abrupt changes in slab geometry, may explain the observed variations in seismogenesis of the DSZs and TSZs. The comparison of our relocated seismicity with the thermal model for the slab beneath Cook Inlet shows that the intermediate-depth earthquakes occur between 500 degrees C and 900 degrees C isotherms. The 2016 Mw 7.1 Iniskin earthquake and its aftershocks are located at approximately 800-900 degrees C. The intricate small-scale variations in different characteristics of the DSZs and intermediate-depth seismicity and their correlations with major geometrical and physical controls can provide insight into what governs the seismogenesis of subduction-induced earthquakes

Nested regional-global seismic tomography and precise earthquake relocation along the Hikurangi subduction zone, New Zealand

SUMMARY Seismic and geodetic examinations of the Hikurangi subduction zone (HSZ) indicate a remarkably diverse and complex system. Here, we investigate the 3-D P-wave velocity structure of the HSZ by applying an iterative, nested regional-global tomographic algorithm. The new model reveals enhanced details of seismic variations along the HSZ. We also relocate over 57 000 earthquakes using this newly developed 3-D model and then further improve the relative locations for 75 per cent of the seismicity using waveform cross-correlation. Double seismic zone characteristics, including occurrence, depth distribution and thickness change along the strike of the HSZ. An aseismic but fast Vp zone separates the upper and lower planes of seismicity in the southern and northern North Island. The upper plane of seismicity correlates with low Vp zones below the slab interface, indicating fluid-rich channels formed on top and/or within a dehydrated crust. A broad low Vp zone is resolved in the lower part of the subducting slab that could indicate hydrous mineral breakdown in the slab mantle. In the northern North Island and southern North Island, the lower plane of seismicity mostly correlates with the top of these low Vp zones. The comparison between the thermal model and the lower plane of seismicity in the northern North Island supports dehydration in the lower part of the slab. The mantle wedge of the Taupo volcanic zone (TVZ) is characterized by a low velocity zone underlying the volcanic front (fluid-driven partial melting), a fast velocity anomaly in the forearc mantle (a stagnant cold nose) and an underlying low velocity zone within the slab (fluids from dehydration). These arc-related anomalies are the strongest beneath the central TVZ with known extensive volcanism. The shallow seismicity (<40 km depth) correlates with geological terranes in the overlying plate. The aseismic impermeable terranes, such as the Rakaia terrane, may affect the fluid transport at the plate interface and seismicity in the overlying plate, which is consistent with previous studies. The deep slow slip events (25–60 km depths) mapped in the Kaimanawa, Manawatu and Kapiti regions coincide with low Vp anomalies. These new insights on the structure along the HSZ highlight the change in the locus of seismicity and dehydration at depth that is governed by significant variations in spatial and probably temporal attributes of subduction zone processes

Insights into Temporal Evolution of Induced Earthquakes in the Southern Delaware Basin Using Calibrated Relocations from the TXAR Catalog (2009-2016)

The Texas Seismological Network (TexNet) has enabled real-time monitoring of induced earthquakes since 2017. Before 2017, location uncertainties and temporal gaps in seismic data obscure correlations across Texas between seismicity and saltwater disposal or hydraulic fracturing. Depth biases also complicate linking anthropogenic stress changes to faults. We relocate 73 M 1.5+ earthquakes from the TXAR catalog (2009-2016) relative to the centroid of a calibrated core cluster consisting of 116 earthquakes from the TexNet catalog post-2020, in the southern Delaware basin south of the Grisham fault zone. Hypocentroidal decomposition relocation reduces spatial uncertainties of the TXAR events to <5 km and provides updated depths. The core cluster has uncertainties less than <300 m and depth constrained from near-source stations and S-P differential times. The majority of relocated TXAR events indicate the triggering of northwest-trending faults at a mean depth of 1 km below sea level, suggesting a causal connection with shallow saltwater disposal and consistency with post-2017 seismicity. Spatiotemporal patterns of pre-2017 seismicity and saltwater disposal highlight initial triggering via pore-pressure stress perturbations from nearby low-volume injections and later from southeastward pressure diffusion along permeable anisotropic conduits and fracture zones. The comparison between pre- and post-2017 seismicity indicates shallow fault reactivation through similar triggering mechanisms since 2009

Seismicity in the western coast of the South Caspian Basin and the Talesh Mountains

We have studied the seismicity of the western margin of the South Caspian Basin (SCB) and the neighbouring Talesh fold and thrust belt. We have used the hypocentroidal decomposition multiple-event location technique to obtain accurate location of events recorded during 2 yr of observation. Data from a temporary seismic network in northwest Iran and other national and regional networks were combined to make an accurate assessment of seismicity in the region. Significant offshore seismicity is observed in a 50-km wide margin of the SCB. East of the Talesh Fault along the Caspian coastline, the depth of seismicity varies from 20 to 47 km. This pattern extends inland about 20–25 km west of the North Talesh Fault. This pattern of seismicity indicates that the basement slab of the South Caspian is undergoing intense seismic deformation as it is underthrusting beneath the northern Talesh, whereas the sedimentary cover deforms aseismically. The seismicity, depths, and previous focal mechanisms of the larger offshore events are consistent with low-angle underthrusting of the South Caspian floor. Within the Talesh, seismicity is mostly concentrated in the northern and southern structural arcs of the range, where deformation is more intense and complicated. Shallow crustal seismicity in the eastern flank of the Talesh is much less intense than in the western flank, where it signifies the deformation of the upper continental crust. One major observation is the lack of any significant N–S alignment of shallow epicentres inside the central Talesh to match the observed right-lateral shear deformation there. This suggests that shear deformation inside the Talesh may have a distributed nature, rather than being concentrated on a single thorough-going fault zone, as the Talesh moves northward relative to the South Caspian. We have determined a new moment tensor solution in the southwestern Talesh, with a dominant N–S trending right-lateral motion, the only solution so far confirming along-strike shear deformation in the Talesh

InSAR observations of construction-induced coastal subsidence on Miami's barrier islands, Florida

This repository contains the data used in Aziz Zanjani et al., 2024. It includes InSAR time-series datasets from the Sentinel-1 satellite, acquired over Miami's barrier islands, Florida. The datasets are divided into two time frames: 2016-2023 and 2019-2023. The files "North_20162023" and "North_20192023" cover the Sunny Isles. The files "South_20162023" and "South_20192023" include displacement data for Surfside and Miami Beach. Aziz Zanjani, F., F. Amelung, A. Piter, K. Sobhan, A. Tavakkoliestahbanati, G.P. Eberli, M. Haghshenas Haghighi, M. Motagh, P. Milillo, S. Mirzaee, A. Nanni, and E. Andiroglu. "InSAR observations of construction-induced coastal subsidence on Miami's barrier islands, Florida" Submitted to Earth and Space Science.

Oxaliplatin disrupts nucleolar function through biophysical disintegration

Platinum (Pt) compounds such as oxaliplatin are among the most commonly prescribed anti-cancer drugs. Despite their considerable clinical impact, the molecular basis of platinum cytotoxicity and cancer specificity remain unclear. Here we show that oxaliplatin, a backbone for the treatment of colorectal cancer, causes liquid-liquid demixing of nucleoli at clinically relevant concentrations. Our data suggest that this biophysical defect leads to cell-cycle arrest, shutdown of Pol I-mediated transcription, and ultimately cell death. We propose that instead of targeting a single molecule, oxaliplatin preferentially partitions into nucleoli, where it modifies nucleolar RNA and proteins. This mechanism provides a general approach for drugging the increasing number of cellular processes linked to biomolecular condensates