We conduct waveform inversion for the 3‐D seismic shear wave (S‐wave) velocity structure in the lowermost mantle near the northern edge of the Pacific large low‐shear‐velocity province (LLSVP). We image a slab‐like high‐velocity anomaly slipping beneath the Pacific LLSVP in the lowermost 200 km of the mantle, extending toward an ultra‐low velocity zone (ULVZ) beneath a point about 2,000 km southwest of Hawaii. Another strong low‐velocity anomaly exists along the edge of the LLSVP just above the slab‐like sheet, 50–200 km above the core‐mantle boundary (CMB). These results suggest in general that (a) slabs can gather ULVZ materials scattered on the CMB and push them into LLSVPs, creating concentrated ULVZs near LLSVP edges, (b) slabs can uplift hot material from the CMB to create strong anomalies along the edges of LLSVPs, and (c) large seismic‐wave velocity contrasts between strong low‐velocity anomalies and slabs create sharp LLSVP boundaries.

There was an ongoing public debate on earthquake forecasting in the early 20th century between two Japanese seismologists, Akitsune IMAMURA and Fusakichi OMORI. In 1905 Imamura pointed out in a magazine article that historically Tokyo had been hit by large earthquakes every 100 years on average. Imamura argued that as the last one was 50 years ago, assuming quasi-periodicity, another one could be expected in the next several tens of years. Imamura's thesis was reported sensationally in several newspaper articles in early 1906. Omori responded by making strong criticisms of Imamura's work in a magazine article. The debate flared up in 1912, and simmered in following years. On Sept. 1, 1923 the Great Kanto earthquake occurred, killing approximately 105,000 persons. Some people regarded the occurrence of the 1923 earthquake as proof that Imamura made a successful prediction and that Omori's criticisms were wrong. This episode has lessons for us even today.

We use waveform inversion to infer high-resolution 3-D models of the S-velocity perturbation delta V-S and the anisotropy parameter delta xi. in the lowermost 400 km of the mantle beneath the northern Pacific. Our inferred models show three prominent features: (i) a widespread positive delta V-S layer with similar to 100 km thickness that exists similar to 250 km above the core-mantle boundary (CMB), which could be due to a bridgmanite to post-perovskite phase transition related to the D '' discontinuity; (ii) distinct positive-delta V-S anomalies with positive delta xi resolved from 100 km to more than 400 km above the CMB, which could be the subducted Izanagi, Farallon, and Telkhinia slabs; (iii) a vertically continuous low-delta V-S anomaly with negative delta xi at the edge of the subducted slab, which we interpret as an upwelling plume induced by slab sinking. We infer the Clapeyron slope of the post-perovskite phase transition in the lowermost mantle beneath the northern Pacific to be 10.2 +/- 1.3 MPa/K, based on the delta V-S gradient as a function of depth for the inferred 3-D V-S structure. Our estimated large positive Clapeyron slope at the CMB suggests vigorous convection in the lowermost mantle.

Software packages for computing seismic traveltimes and raypaths in an isotropic, spherically symmetric, Earth model are well known and widely used. However, even though the theory for transversely isotropic (TI), spherically symmetric, models has been known since the late 1960s, readily available programs for traveltime calculations are restricted to isotropic models. We have developed a new software package, ANISOtime, for computing seismic traveltimes and raypaths in laterally homogeneous, TI, spherical media. This package calculates traveltime tables for both immediate and subsequent use. ANISOtime has both graphical user interface and command-line inter-face modes. The package is available for free public download. As it offers cross -plat-form compatibility through Java 8, it runs on Windows, macOS, Unix, and Linux.

Although previous tomographic studies found a large low S-velocity province (LLSVP) in the lowermost mantle beneath the Pacific, due to a lack of resolution it was unclear whether the LLSVP consists of clusters of small-scale low-velocity anomalies or large-scale anomalies. We recently deployed a seismic-array in Thailand which provides a dataset with wide azimuthal coverage of the western Pacific LLSVP. We analyze the new dataset using waveform inversion, and find high-velocity anomalies extending vertically to a height of similar to 400 km above the core-mantle boundary (CMB) beneath the Philippine Sea and small-scale low-velocity patches with a diameter of similar to 300 km at the CMB beneath New Guinea. The locations of the high-velocity anomalies are consistent with the past Izanagi-plate subduction boundary, and the low-velocity anomalies can be interpreted as a small-scale plume cluster. Hence we conclude that vertical flow (upwelling plumes and downwelling of slabs) is dominant in the lowermost mantle beneath the western Pacific region.

In the United States, through nation-wide discussions, the procedures for handling allegations of research misconduct are now well established. Procedures are geared toward carefully treating both complainants and respondents fairly in accordance with the US framework. Other countries, which have their own cultural and legal framework, also need fair and legally compatible procedures for conducting investigations of allegations of research misconduct. Given the rapid growth of international collaboration in research, it is desirable to have a global standard, or common ground, for misconduct investigations. Institutions need clear guidance on important subjects such as what information should be included in the investigation reports, how the investigation committee should be organized once research misconduct allegation has been received, how to conduct the investigation, how the data and information obtained should be taken as evidence for vs. against misconduct, and what policies the investigation committee should follow. We explore these issues from the viewpoint of members of committees investigating accusations of research misconduct (hereafter referred to as "investigation committees") as well as persons overseeing the committees in Japan. We hope to engender productive discussions among experts in misconduct investigations, leading to a formulation of international standards for such investigation.

The origin of velocity anomalies in the lowermost mantle, e.g., thermal, chemical, or due to phase transition, is still debated. Intrinsic seismic attenuation (Q) strongly depends on temperature, thus could provide additional constraints on the thermal contribution to seismic anomalies in the lowermost mantle. In this study, we investigate the radial (1-D) elastic (Vs) and anelastic (Q) structure of the lowermost mantle beneath Central America and the Caribbean using waveform inversion. We use ~50 intermediate and deep focus earthquakes in South America recorded at the USArray and other small networks between 2004–2015. Waveforms are filtered between 12.5–200 s and cut ~20 s before the arrival of the direct S phase, and ~60 s after the arrival of the ScS phase. We use the S phase as a reference phase to correct for the effects of the structure near the events and receivers on the travel-time and amplitude of ScS waveforms (Konishi et al., 2017). Synthetic tests show that we can resolve the 1-D Q and Vs structures of the lowermost mantle, with some amount of tradeoff between them. In an attempt to reduce the tradeoff between the Vs and Q structure, we perform iterative inversion inferring in a first step the Vs structure only, and in a second step the Vs and Q structures simultaneously.

Travel time tomography studies have reported various modes of subduction of slabs around the mantle transition zone, but the causes of this variability are still controversial. In order to place additional constraints on the style of subduction in and near the mantle transition zone, we apply waveform inversion to S wave triplications due to the 410‐ and 660‐km discontinuities, and infer the regional three‐dimensional S velocity structure in the depth range 370–820 km beneath Central America and the Gulf of Mexico. We use ~3,400 transverse component records at epicentral distances 17–30° from 20 intermediate focus earthquakes beneath Central America recorded at stations of the USArray and other smaller networks. We filter the records between 20 and 100 s, and use the portions of the waveforms from 10 s before to ~40–80 s after the arrival of the direct S wave, thereby including the S wave triplications while excluding the sS depth phase. We correct the data for the structure above our target region using previous S velocity models, and we show that the results of the inversion do not depend heavily on which correction is used. Resolution tests confirm that we can resolve small‐scale structure in the target region. Our inferred models show that the Cocos slab penetrates into the lower mantle, but with important variations along the Middle America Trench in the subduction style of the slab. We suggest that this variability could be due to the thermal structure of the Cocos slab, and to the interaction of the slab with a possible lower mantle plume.

The D″ region, lowermost several hundred kilometers of the Earth's mantle immediately above the core-mantle boundary (CMB), is the thermal boundary layer, and the solidus of its constituent materials is thought to be close to the mantle geotherm. Therefore, vertical and lateral variations of temperature and chemical composition associated with Earth's thermal evolution are expected. The 3-D S-wave velocity structure of D″ beneath Eurasia has ever been inferred by traveltime tomography (e.g., Grand 2002) or global waveform inversion studies (e.g., French & Romanowicz 2014) not yet by localized waveform inversion ones. We infer the 3-D S-wave velocity structure of D″ beneath Eurasia, using localized waveform inversion methods (Kawai et al. 2014). We use waveform data obtained from the National Research Institute for Earth Science and Disaster Prevention F-net and Observation & Research Facilities for European Seismology (ORFEUS). Our dataset consists of about 4,200 transverse component of broadband body-wave seismograms observed at Japan for 4 intermediate earthquakes occurred in Europe, and European stations for 137 intermediate and deep events occurred beneath the western Pacific subduction zone. We use waveforms in time window including S and ScS phases. The results of the synthetic resolution test (checkerboard test) indicate that our methods and dataset can resolve S-wave velocity structure in the target region vertically 50 km and laterally 5°. We obtain 3-D S-wave velocity models showing two distinct low-velocity anomalies about 4 per cent slower than the Preliminary Reference Earth Model (PREM). We interpret the low-velocity anomaly which is located at the west of the target region as “Perm Anomaly”

As recent waveform inversion studies to determine 3-D Earth structure are increasingly using data in shorter period ranges, the sensitivity of the inversion results to source parameters, the source time function (STF) in particular, will increase. In this study we redetermine the centroid and moment tensor (CMT) solutions for 41 deep- and intermediate-earthquakes beneath South America, using only body-wave data in the same period range used in localized waveform inversion. We then redetermine the STFs of 35 of these events by stacking the displacement of P-waves. We use four slightly different methods to obtain four sets of redetermined source parameters. We find that all four sets of redetermined source parameters generally agree with the GCMT solutions, but the STF durations are systematically shorter than those for the GCMT solutions, particularly for events with moment-magnitudes larger than 6.5. We then apply the four sets of redetermined source parameters for the 35 events to localized waveform inversion for the 3-D seismic velocity structure of the D″ region beneath Central America and the Caribbean using PREM as the 1-D initial model. We improve the 3-D structure (as shown by improved variance reduction), particularly after redetermination of moment tensors and STFs. The velocity patterns of the four new 3-D structure models for the D″ region inferred by inversions using the redetermined source parameters do not differ significantly from those inferred using the GCMT source parameters. However, the amplitude of the lateral heterogeneity decreases when synthetics for the redetermined STFs are used.

Many research topics in geophysics have important implications for public policy; two examples considered here are climatology and attempts to predict future seismic ground motion. A common feature of these and other fields of geophysics is that much work on developing mathematical models is being conducted, but efforts on testing and validating these models and on evaluating their uncertainties has tended to lag. Modelers should do a better job of making clear what is known (including realistic estimates of the uncertainties) and what is not known. Public policy regarding climate change and earthquake hazard mitigation must be decided now, notwithstanding the limitations of the state of the art of modeling. Such policy decisions necessarily require compromise and the search for consensus. It is essential to distinctly separate scientific research and decisions on public policy, so that the former is conducted strictly following best practices of science without compromises or attempts to force consensus to be reached.

Global cooperation in clinical research maximizes access to patients, enables resource sharing and increases the applicability of research findings.Yet academic trials are rarely