Parkfield earthquake of June 28, 1966: Magnitude and source mechanism

The Parkfield earthquake of June 28, 1966 (04:26:12.4 GMT) is studied using short-period and long-period teleseismic records. It is found that (1) Mb = 5.8 and Ms = 6.4 as compared to Mb = 5.4 and Ms = 5.4 for the foreshock (04:08:54), (2) both the Rayleigh and Love wave radiation patterns conform to those of a double couple at a depth of about 8.6 km, (3) the main shock can be represented by a series of shocks separated in space and time. The near-field strong-motion data support the last conclusion. Based on strong-motion seismograms, and the surficial evidences of the dimensions of the fault, the energy is found to be 10^(21) ergs

Source mechanism of February 4, 1965, Rat Island earthquake

The Rat Island earthquake of February 4, 1965 (origin time 05h 01m 21.8s, h = 40 km), is one of the largest earthquakes recorded in recent years. On the basis of the radiation patterns and the amplitudes of the great circle Rayleigh and Love waves, the earthquake is found to have the following characteristics: fault plane dip, 18°; fault plane dip direction, N19°E; rupture propagation direction, N51°W; rupture propagation velocity, 4.0 km/sec; fault length, 500 km; moment, 1.4 × 10^(29) dynes cm; stress drop, 30 bars; and average dislocation, 2.5 meters. It is interesting to observe that the attitude of the fault plane and the general features of this earthquake are similar to those of the 1963 Kurile earthquake (Kanamori, 1970a) and the 1964 Alaskan earthquake (Kanamori, 1970b). The first 35 sec of P waves were also well recorded at many stations. The wave forms suggest a multiple-event nature of the earthquake for at least the initial 35 sec. By using the relative location method, the events were located progressively south of the initial hypocenter. It seems plausible that the earthquake started off at depth, first propagated southward, and then westward along the Aleutian arc. Owing to the long-period nature of the surface waves, only the average feature of the fault is seen, and P waves reveal some of the detailed initial behavior

PP and crustal structure

Haskell's formulation for reflection of P waves at the base of a solid crust is extended to include overlying liquid layers. Normalized displacement and the phase shift at the base of the crust as a function of angle of incidence and frequency are calculated for two continental models and an oceanic model. Complex reflection coefficients are inverse Fourier transformed to the time domain to show the change of pulse shape upon reflection. These time traces show that the water layer of the oceanic model causes the main difference between continental and oceanic reflections. Sample seismograms from a deep shock were compared to the theoretical records; they were found to be consistent. It is concluded that the amplitude ratio PP/P as a function of frequency obtained from seismograms can be used to decipher the detailed structure at the point of reflection only after the radiation pattern of the source, attenuation of waves during propagation, and crustal transmission response at the receiver are properly taken into account

Bounds for phylogenetic network space metrics

Phylogenetic networks are a generalization of phylogenetic trees that allow for representation of reticulate evolution. Recently, a space of unrooted phylogenetic networks was introduced, where such a network is a connected graph in which every vertex has degree 1 or 3 and whose leaf-set is a fixed set X of taxa. This space, denoted N(X)N(X) , is defined in terms of two operations on networks—the nearest neighbor interchange and triangle operations—which can be used to transform any network with leaf set X into any other network with that leaf set. In particular, it gives rise to a metric d on N(X)N(X) which is given by the smallest number of operations required to transform one network in N(X)N(X) into another in N(X)N(X) . The metric generalizes the well-known NNI-metric on phylogenetic trees which has been intensively studied in the literature. In this paper, we derive a bound for the metric d as well as a related metric dNNIdNNI which arises when restricting d to the subset of N(X)N(X) consisting of all networks with 2(|X|−1+i)2(|X|−1+i) vertices, i≥1i≥1 . We also introduce two new metrics on networks—the SPR and TBR metrics—which generalize the metrics on phylogenetic trees with the same name and give bounds for these new metrics. We expect our results to eventually have applications to the development and understanding of network search algorithms

Terrane‐controlled crustal shear wave splitting in Taiwan

Taiwan is the result of arc‐continent collision associated with the convergence of the Philippine Sea plate with the eastern Eurasian plate continental margin. The locus of deformation is found in eastern Taiwan in the form of mountain building (Central Range) with underlying thickened lithosphere. Rapid tectonic exhumation in the Central Range has uncovered low‐to‐high‐grade metamorphic rocks marked by steep cleavage. We carried out a crustal seismic anisotropy study across Taiwan, producing a database of over 27,000 local earthquake shear wave splitting measurements. Additionally, we carried out rock physics measurements of metamorphic outcrop samples to quantify shear wave rock anisotropy. We produced a map of station‐averaged splitting measurements across Taiwan. Patterns of fast shear wave directions correlate with tectonic terranes produced by plate convergence. Deformation‐related mineral‐preferred orientation in the metamorphic rocks produces a significant amount of the crustal anisotropy in the Taiwan collision zone

Primary Osteoarthritis Early Joint Degeneration Induced by Endoplasmic Reticulum Stress Is Mitigated by Resveratrol

Increasing numbers of people are living with osteoarthritis (OA) due to aging and obesity, creating an urgent need for effective treatment and preventions. Two top risk factors for OA, age and obesity, are associated with endoplasmic reticulum (ER) stress. The I-ERS mouse, an ER stress-driven model of primary OA, was developed to study the role of ER stress in primary OA susceptibility. The I-ERS mouse has the unique ability to induce ER stress in healthy adult articular chondrocytes and cartilage, driving joint degeneration that mimics early primary OA. In this study, ER stress-induced damage occurred gradually and stimulated joint degeneration with OA characteristics including increased matrix metalloproteinase activity, inflammation, senescence, chondrocyte death, decreased proteoglycans, autophagy block, and gait dysfunction. Consistent with human OA, intense exercise hastened and increased the level of ER stress-induced joint damage. Notably, loss of a critical ER stress response protein (CHOP) largely ameliorated ER stress-stimulated OA outcomes including preserving proteoglycan content, reducing inflammation, and relieving autophagy block. Resveratrol diminished ER stress-induced joint degeneration by decreasing CHOP, TNFα, IL-1β, MMP-13, pS6, number of TUNEL-positive chondrocytes, and senescence marker p16 INK4a. The finding, that a dietary supplement can prevent ER stressed-induced joint degeneration in mice, provides a preclinical foundation to potentially develop a prevention strategy for those at high risk to develop OA

Terrane‐controlled crustal shear wave splitting in Taiwan

Taiwan is the result of arc‐continent collision associated with the convergence of the Philippine Sea plate with the eastern Eurasian plate continental margin. The locus of deformation is found in eastern Taiwan in the form of mountain building (Central Range) with underlying thickened lithosphere. Rapid tectonic exhumation in the Central Range has uncovered low‐to‐high‐grade metamorphic rocks marked by steep cleavage. We carried out a crustal seismic anisotropy study across Taiwan, producing a database of over 27,000 local earthquake shear wave splitting measurements. Additionally, we carried out rock physics measurements of metamorphic outcrop samples to quantify shear wave rock anisotropy. We produced a map of station‐averaged splitting measurements across Taiwan. Patterns of fast shear wave directions correlate with tectonic terranes produced by plate convergence. Deformation‐related mineral‐preferred orientation in the metamorphic rocks produces a significant amount of the crustal anisotropy in the Taiwan collision zone

The innermost region of AGN tori: implications from the HST/NICMOS Type 1 point sources and near-IR reverberation

Spatially resolving the innermost torus in AGN is one of the main goals of its high-spatial-resolution studies. This could be done in the near-IR observations of Type 1 AGNs where we see directly the hottest dust grains in the torus. We discuss two critical issues in such studies. Firstly, we examine the nuclear point sources in the HST/NICMOS images of nearby Type 1 AGNs, to evaluate the possible contribution from the central putative accretion disk. After a careful subtraction of host bulge flux, we show that near-IR colors of the point sources appear quite interpretable simply as a composite of a black-body-like spectrum and a relatively blue distinct component as expected for a torus and an accretion disk, respectively. Our radiative transfer models for clumpy tori also support this simple two-component interpretation. The observed near-IR colors suggest a fractional accretion disk contribution of ~25% or less at 2.2 micron. Secondly, we show that the innermost torus radii as indicated by the recent near-IR reverberation measurements are systematically smaller by a factor of ~3 than the predicted dust sublimation radius with a reasonable assumption for graphite grains of sublimation temperature 1500 K and size 0.05 micron in radius. The discrepancy might indicate a much higher sublimation temperature or a typical grain size being much larger in the innermost tori, though the former case appears to be disfavored by the observed colors of the HST point sources studied above. The near-IR interferometry with a baseline of ~100 m should be able to provide the important, independent size measurements, based on the low accretion disk contribution obtained above.Comment: accepted for publication in A&

Onshore/ offshore wide-angle deep seismic profiling in Taiwan

In summer 1995, in collaboration with the deep multi-channel seismic profiling project around the island of Taiwan, anonshore-offshore wide-angle deep seismic profiling experiment was conducted in Taiwan. The results are expected to provide the first complete seismic images of the deep crustal structure for a better understanding of the Taiwan orogeny and subduction-collision system. The experiment consists of three profiles, one along each of the central and southern cross-island highways and another on the south-link highway of the island. For the first two lines, 35 three-component portable seismographs were deployed along each of the 116 and 135 km-long profiles onshore, with airgun shots being fired at distances eastward form the east coast of up to 133 km and 170 km, respectively. On the third line, 6 stations were deployed along the 20 km-long profile. For this line, the R/V Ewing provided shots from the Philippine Sea westward to the eastern coast of the Hengchun Peninsula and then from the western coast of the Hengchun Peninsula westward away from Taiwan. The total length of the third line was about 310 km. The average station intervals were about 4 km. The preliminary results along the three profiles show a very thick crust beneath Taiwan. In addition, the velocity structures show that lateral variation of velocity in the upper crust is generally larger than that in the lower crust and uppermost mantle. Large thickness variations in the crust were also obtained. The crustal thickness beneath Taiwan diminishes gradually toward the west, but dramatically toward the east. The topographic high is not well associated with the crustal thickness. The thickest crust is to the east of the central mountain range, which may indicate that Taiwan has not yet reached its isostatic equilibrium. In this paper, the preliminary results along the southern cross-island profile are given as an example. Detailed results of the three profiles will be given elsewhere