Theoretical and empirical evidence suggests that peoples' perceptions of household seismic adjustments, in addition to their perceptions of earthquakes themselves, should predict the likelihood that seismic adjustments are performed. However, little research has been done to address this issue. While recent research has found peoples' perceptions of the effectiveness of household adjustments to influence adjustment levels, people's perceptions of inconvenience of household seismic adjustments - namely the cost, time effort, required cooperation and required knowledge involved in making these adjustments - have been found to not influence seismic adjustment. However, this study did find that the higher the perceived inconveniences of an adjustment, the less likely people are to perform those adjustments. As a second area of investigation, a survey was given to subjects in an understudied risk population (residents living along the Wasatch Fault Line that runs through the state of Utah) to compare Utahns to Washingtonians and Californians. The survey revealed that although California residents have the highest risk perceptions and the most previous earthquake experience, they rank lower than Washington and Utah residents in terms of how much they think, talk, and gather information about earthquakes. Implications of both areas of research are discussed.

On September 16, 2015, a Mw 8.3 earthquake struck offshore of the north-central Chile coast with a fault-rupture length of approximately 150 km. The earthquake triggered a tsunami that impacted 500 km of coastline from Huasco (28.5°S) to San Antonio (33.5°S), registering as much as 4.5 m on the tide gauge at Coquimbo (30.0°S) with run-up heights >10 m at a few exposed locations between Limarí (30.7°S) and Coquimbo. The tsunami provided an invaluable opportunity to examine the nature of tsunami deposit evidence in a semi-arid, siliciclastic environment, where settings suitable for the preservation of tsunami sedimentation are scarce, thereby improving our ability to identify such evidence in the geologic record. Using before-and-after-tsunami satellite imagery and post-tsunami coastal surveys, we targeted one of the few low-energy depositional terrestrial environments in the tsunami-affected area that had a high potential to preserve the 2015 tsunami deposit and older events: the Pachingo marsh in Tongoy Bay (30.3°S). We employed field and laboratory methods to document the 2015 tsunami deposit and discovered sedimentological evidence of previous tsunami inundation of the site. The 2015 tsunami deposit and an older sand bed ~10 cm lower in the stratigraphy exhibit similar sedimentological characteristics. Both sand beds are composed of poorly to moderately sorted, gray-brown, fine- to medium-grained sand and are distinct from underlying and overlying organic-rich silty sediments. The sand beds are thinner (from ~20 cm to <1 cm) and finer (from medium- to fine-grained sand) at more inland locations, and fine upward. However, the older sand bed extends over 150 m farther inland than the 2015 tsunami deposit. To explore the differences in the offshore ruptures that generated the tsunamis that deposited each sand bed, we employed an inverse sediment transport model (TSUFLIND). Our field survey, sedimentological data, and modeling results infer that the older sand bed preserved at the Pachingo marsh field site was produced by a larger tsunami than the 2015 tsunami. Anthropogenic evidence (copper smelter waste) along with Cs137 and Pb210 dating constrains the magnitude and age of the older sand bed to the last 130 years. Based on historical analysis of recent tsunamis that impacted the Pachingo marsh region, we infer a widespread tsunami in 1922 is the best candidate for depositing the older sand bed at our site, providing first geologic evidence of pre-2015 tsunami inundation along the north-central Chile coast. / Master of Science / On September 16, 2015 a segment of the Chilean subduction zone ruptured off the coast of north-central Chile producing a magnitude 8.3 earthquake. The earthquake created a tsunami that impacted 500 km of coastline and created waves measuring 4.5 m on the tide gauge at Coquimbo (30.0°S) with waves reaching inland to heights >10 m at a few exposed locations. The 2015 event in north-central Chile provided a unique opportunity to study tsunami deposits in semi-arid, sand-dominated environment where preservation of tsunami deposits within coastal sediments is rare, helping improve our ability to identify this type of evidence in the sedimentary record. Using before-and-after-tsunami satellite imagery and post-tsunami coastal surveys, we targeted a marsh in the tsunami-affected area that was capable of preserving the 2015 tsunami deposit and older events: the Pachingo marsh in Tongoy Bay (30.3°S). We employed field and laboratory methods to document the 2015 tsunami deposit and discovered evidence of previous tsunami overwash at the site within the sediments of the marsh. Our field work observations and sedimentary data revealed that in addition to the 2015 tsunami deposit, the site contained an older, anomalous sand bed that we infer to be a tsunami based on its similarity to the modern deposit at the site. Our modeling results suggest that the older sand bed was deposited by a tsunami larger than the 2015 tsunami. Based on historical analysis of recent tsunamis that impacted the Pachingo marsh region, we infer a tsunami in 1922 is the best candidate for depositing the older sand bed at our site. This discovery provides the first evidence of tsunami sediments from pre-2015 tsunami inundation along the north-central Chile coast.

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Thesis advisor: John E. Ebel / Power-law scaling relationships concerning the earthquake frequency-magnitude distribution and the fractal geometry of spatial seismicity patterns may provide applications to earthquake forecasting and earthquake hazard studies. Past studies on the fractal characteristics of seismic phenomena have observed spatial and temporal differences in earthquake clustering and b value in relation to fractal dimension value. In this thesis, an investigation of the spatiotemporal seismicity patterns in southern California for the years 1982 to 2020 was conducted. The range and temporospatial distribution of b and D2 values for earthquake hypocenters contained in the Southern California Earthquake Data Center catalogue were calculated and shown in time series and spatial distribution maps. b values were calculated using both the Least SquaresMethod and the Maximum Likelihood Method while D2 values were calculated for length scales between 1 km to 10 km. A set of b and D2 values were calculated after declustering for foreshocks and aftershocks using Gardner and Knopoff’s declustering algorithm. b values decreased while D2 values increased on the dates of M > 6.0 earthquakes, whereas b values increased and D2 values decreased on the dates after M > 6.0 earthquakes. Declustering results suggest an influence of earthquake aftershocks to increase D2 values while decreasing b values. The role for b values and D2 values to delineate both the temporal and spatial extent of aftershock sequences for large earthquakes may prove to have an application in earthquake hazard studies. / Thesis (MS) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Thesis. 1975. Sc.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography: leaves 358-387. / Sc.D.

Earthquake-induced liquefaction of saturated soils and seismic compression of unsaturated soils are major sources of hazard to infrastructure, as attested by the wholesale condemnation of neighborhoods surrounding Christchurch, New Zealand. The hazard continues to grow as cities expand into liquefaction- and seismic compression-susceptible areas hence accurate evaluation of both hazards is essential. The liquefaction evaluation procedure presented herein is based on dissipated energy and an SPT liquefaction/no-liquefaction case history database. It is as easy to implement as existing stress-based simplified procedures. Moreover, by using the dissipated energy of the entire loading time history to represent the demand, the proposed procedure melds the existing stress-based and strain-based liquefaction procedures in to a new, robust method that is capable of evaluating liquefaction susceptibility from both earthquake and non-earthquake sources of ground motion. New relationships for stress reduction coefficient (r_d) and number of equivalent cycles ($n_{eq}$) are also presented herein. The r_d relationship has less bias and uncertainty than other common stress reduction coefficient relationships, and both the $n_{eq}$ and $r_d$ relationships are proposed for use in active tectonic and stable continental regimes. The $n_{eq}$ relationship proposed herein is based on an alternative application of the Palmgren-Miner damage hypothesis, shifting from the existing high-cycle, low-damage fatigue framework to a low-cycle framework more applicable to liquefaction analyses. Seismic compression is the accrual of volumetric strains caused by cyclic loading, and presented herein is a "non-simplified" model to estimate seismic compression. The proposed model is based on a modified version of the Richart-Newmark non-linear cumulative damage hypothesis, and was calibrated from the results of drained cyclic simple shear tests. The proposed model can estimate seismic compression from any arbitrary strain time history. It is more accurate than other "non-simplified" seismic compression estimation models over a greater range of volumetric strains and can be used to compute number-of-equivalent shear strain cycles for use in "simplified" seismic compression models, in a manner consistent with seismic compression phenomenon. / Ph. D.

The Charleston earthquake of 1886 was one of the largest shocks to occur on the eastern coast of North America. The geological cause has long been a controversial issue and a variety of source models have been proposed. Previous potential field modeling and reinterpretation of seismic reflection and well data collected in the early 1980s indicate that the crust between approximately 1 and 4.5 km depth is comprised primarily of Mesozoic mafic rocks, with extensive faulting that is spatially coincident with modern seismicity in the epicentral area (Chapman and Beale, 2010). This thesis proposes a new and testable hypothesis concerning the fault source of the 1886 shock that is very different from all previous interpretations. It is based on data collected during 2011-2012 from a local seismic network deployment in the immediate epicentral area. The 8-station temporary network was designed to better constrain earthquake hypocenter locations and focal mechanisms. Hypocenter locations of 134 earthquakes indicate a south-striking, west-dipping seismogenic zone in the upper 12 km of the crust. Over 40% of the 66 well-constrained focal mechanisms show reverse faulting on approximately north-south trending nodal planes, consistent with the orientation of the tabular hypocenter distribution. I offer the following hypothesis: The 1886 shock occurred by compressional reactivation of a major, south-striking, west-dipping early Mesozoic extensional fault. The modern seismicity can be regarded as a long-term aftershock sequence that is outlining the 1886 damage zone. Variability of shallow focal mechanisms is due to the complex early Mesozoic fault structure in the upper 4-5 km. / Master of Science

Magnitude Scaling Factors (MSF) account for the durational effects of strong ground shaking on the inducement of liquefaction within the simplified liquefaction evaluation procedure which is the most commonly used approach for assessing liquefaction potential worldwide. Within the context of the simplified procedure, the spatial variation in the seismic demand imposed on the soil traditionally has been assumed to be solely a function of the spatial variation of the peak amplitude of the ground motions and the characteristics of the soil profile. Conversely, MSF have been solely correlated to earthquake magnitude. This assumption fails to appreciate the inverse correlation between the peak amplitude of ground motions and strong ground motion duration, and thus MSF would seemingly vary spatially. The combination of well-documented liquefaction response during the Darfield and Christchurch, New Zealand, earthquakes, densely-recorded ground motions for the events, and detailed subsurface characterization provides an unprecedented opportunity to investigate the significance of the spatial variation of MSF on the inducement of liquefaction. Towards this end, MSF were computed at 15 strong motion recording station sites across Christchurch and its surroundings using two established approaches. Trends in the site and spatial variation of the MSF computed for both the Darfield and Christchurch earthquakes are scrutinized and their implications on liquefaction evaluations are discussed. / Master of Science

The double difference earthquake location algorithm, implemented in the program HYPODD, was used to relocate a data set of approximately 1000 earthquakes in the eastern Tennessee seismic zone (ETSZ), using a recently developed velocity model. The double difference algorithm is used to calculate accurate relative hypocenter locations by removing the effects of un-modeled velocity structure. The study examines the earthquake hypocenter relocations in an effort to resolve fault orientations and thereby gain insights into the tectonics of the seismic zone. The analysis involves visual comparison of three-dimensional perspective plots of the hypocenter relocations oriented according to focal mechanism nodal planes derived from events within several, dense clusters of earthquakes. The northwestern boundary of the seismic zone corresponds to the steep magnetic gradient of the New York-Alabama lineament. The double-difference relocations reinforced previous interpretations of a vertical boundary between seismic and relatively aseismic crust at that location. Areas at the northeastern and southwestern ends of the ETSZ exhibit northwest trending hypocenter alignments, which are perpendicular to the overall northeastern trend of the seismic zone. These alignments agree with focal mechanism nodal plane orientations and are interpreted as seismogenic faults. In the central, most seismically active portion of the ETSZ, relocations appear to indicate a diffuse zone of hypocenters that are west-striking and north-dipping. The orientation of this zone of earthquake hypocenters is consistent with an existing seismic reflection profile that images mid to upper crustal reflectors with apparent dips of approximately 35 degrees to the north. The interpreted fault planes are all consistent with an east-northeast oriented, sub-horizontal maximum regional compressive stress, consistent with findings in previous studies. / Master of Science