Comparison of geodetic and geologic data from the Wasatch region, Utah, and implications for the spectral character of Earth deformation at periods of 10 to 10 million years

Abstract

[1] The Wasatch fault and adjacent fault zones provide an opportunity to compare present-day deformation rate estimates obtained from space geodesy with geologic displacement rates over at least four temporal windows, ranging from the last millennium up to 10 Myr. The three easternmost GPS sites of the Basin and Range Geodetic Network (BARGEN) at this latitude define a $130-km-wide region spanning three major normal faults extending east-west at a total rate of 2.7 ± 0.4 mm/yr, with an average regional strain rate estimated to be 21 ± 4 nstrain/yr, about twice the Basin and Range average. On the Wasatch fault, the vertical component of the geologic displacement rate is 1.7 ± 0.5 mm/yr since 6 ka, <0.6 mm/yr since 130 ka, and 0.5-0.7 mm/yr since 10 Ma. However, it appears likely that at the longest timescale, rates slowed over time, from 1.0 to 1.4 mm/yr between 10 and 6 Ma to 0.2 to 0.3 mm/yr since 6 Ma. The cumulative vertical displacement record across all three faults also shows time-variable strain release ranging from 2 to 4 mm/yr since 10 ka to <1 mm/yr averaged over the past 130 kyr. Conventional earthquake recurrence models (''Reid-type'' behavior) would require an accordingly large variation in strain accumulation or loading rate on a 10-kyr timescale, for which there appears to be no obvious geophysical explanation. Alternatively, seismic strain release, given a wide range of plausible constitutive behaviors for frictional sliding, may be clustered on the 10-kyr timescale, resulting in the high Holocene rates, with comparatively low, uniform strain accumulation rates on the 100-kyr timescale (''Wallace-type'' behavior). The latter alternative, combined with observations at the million-year timescale and the likelihood of a significant contribution of postseismic transients, implies maxima of spectral amplitude in the velocity field at periods of $10 Myr (variations in tectonic loading), $10 kyr (clustered strain release), and of 100 years (postseismic transients). If so, measurements of strain accumulation and strain release may be strongly timescaledependent for any given fault system.

Irregular earthquake cycle along the southern Tianshan front, Aksu area, China

“…Similar aperiodic behavior was reported along the Dead Sea Fault zone [Marco et al, 1996]. Other examples of long-term analysis of seismic activity using historical catalogs [Ambraseys, 1989;Vere-Jones and Ozaki, 1982;Xu and Deng, 1996;Goes, 1996], paleoseismologic data [Jacoby et al, 1998;Grant and Sieh, 1995;Marco et al, 1996;Wells et al, 1999], geomorphological data [Ritz et al, 2003], or geodesic and geologic data [Friedrich et al, 2003] show that periods of activity can alternate with periods of quiescence along a single fault or a group of faults and that many fault zones exhibit temporal earthquake clustering [Pirazzoli et al, 1996]. These observations suggest that a representative record of the long-term behavior of a fault zone may require a knowledge of all strong earthquakes over period exceeding 10,000 years [ Van der Woerd et al, 2002].…”

Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation

“…Thermochronologic data support slip rates of 3 -7 mm/a as typical for many Cordilleran core complexes [e.g., John and Foster, 1993;Foster and John, 1999, and references therein;Brady, 2002] although Carter et al [2004] interpreted U-Th/He data to indicate that very high slip rates ($30 mm/a) occurred during the final stage of exhumation at the Harcuvar Mountains core complex. Our results from Sierra Mazatán add to a growing database that suggests that faults at many Cordilleran core complexes slipped at rates comparable to the largest normal faults active today, including Holocene slip rates of 1.0-1.7 mm/a on the Wasatch fault, Utah [e.g., Friedrich et al, 2003] and Holocene slip rates of 2.5 -4.0 mm/a in the Gulf of Corinth, Greece [Collier et al, 1998]. Therefore, long-term slip rates for the Sierra Mazatán, as well as many other core complexes, do not appear to be significantly different from rates at the largest active normal faults.…”

Patterns of Quaternary uplift of the Corinth rift southern border (N Peloponnese, Greece) revealed by fluvial landscape morphometry

“…Indeed, GPS measurements in the Corinth gulf area indicate current rates ranging from < 5 mm year -1 at the eastern end of the rift to 11 mm year -1 at the height of Xylokastro and 16 mm year -1 in the western rift (Avallone et al, 2004;Nyst and Thatcher, 2004;Bernard etal., 2006). However, beyond the fact that the E-W variation of these rates does not superpose with long-term variations showing maximum total extension in the central rift (Bell et al, 2011), the question of how, if ever, geologically instantaneous GPS rates may compare with long-term averaged rates is still debated (e.g., Friedrich et al, 2003;Bell et al, 2011).…”