Seismic Wave Propagation in Stratified Media

Seismic Wave Propagation in Stratified Media presents a systematic treatment of the interaction of seismic waves with Earth structure. The theoretical development is physically based and is closely tied to the nature of the seismograms observed across a wide range of distance scales – from a few kilometres as in shallow reflection work for geophysical prospecting, to many thousands of kilometres for major earthquakes. A unified framework is presented for all classes of seismic phenomena, for both body waves and surface waves. Since its first publication in 1983 this book has been an important resource for understanding the way in which seismic waves can be understood in terms of reflection and transmission properties of Earth models, and how complete theoretical seismograms can be calculated. The methods allow the development of specific approximations that allow concentration on different seismic arrivals and hence provide a direct tie to seismic observations

Planning and Managing Scientific Research

Although there are many books on project management, few address the issues associated with scientific research. This work is based on extensive scientific research and management experiences and is designed to provide an introduction to planning and managing scientific research for the beginning researcher. The aim is to build an understanding of the nature of scientific research, and the way in which research projects can be developed, planned and managed to a successful outcome. The book is designed to help the transition from being a member of a research team to developing a project and making them work, and to provide a framework for future work. The emphasis of the book is on broadly applicable principles that can be of value irrespective of discipline. It should be of value to researchers in the later stages of Ph.D. work and Postdoctoral workers, and also for independent researchers

Seismic Wave Propagation in Stratified Media

Seismic Wave Propagation in Stratified Media presents a systematic treatment of the interaction of seismic waves with Earth structure. The theoretical development is physically based and is closely tied to the nature of the seismograms observed across a wide range of distance scales – from a few kilometres as in shallow reflection work for geophysical prospecting, to many thousands of kilometres for major earthquakes. A unified framework is presented for all classes of seismic phenomena, for both body waves and surface waves. Since its first publication in 1983 this book has been an important resource for understanding the way in which seismic waves can be understood in terms of reflection and transmission properties of Earth models, and how complete theoretical seismograms can be calculated. The methods allow the development of specific approximations that allow concentration on different seismic arrivals and hence provide a direct tie to seismic observations

Planning and Managing Scientific Research

Although there are many books on project management, few address the issues associated with scientific research. This work is based on extensive scientific research and management experiences and is designed to provide an introduction to planning and managing scientific research for the beginning researcher. The aim is to build an understanding of the nature of scientific research, and the way in which research projects can be developed, planned and managed to a successful outcome. The book is designed to help the transition from being a member of a research team to developing a project and making them work, and to provide a framework for future work. The emphasis of the book is on broadly applicable principles that can be of value irrespective of discipline. It should be of value to researchers in the later stages of Ph.D. work and Postdoctoral workers, and also for independent researchers

The Significance of Long-Period Ground Motion at Regional to Teleseismic Distances From the 610-km Deep Mw 8.3 Sea of Okhotsk Earthquake of 24 May 2013

The 24 May 2013 earthquake beneath the Sea of Okhotsk (610 km,Mw8.3) producedsignificant ground motion across the whole span of the Japanese islands, from 1,300‐to 4,200‐kmepicentral distance. The largest shaking was concentrated along the back‐arc side of the subductionzone, which is the opposite of the normal pattern for deep earthquakes in the Pacific slab. Observationsfrom the dense Hi‐net and F‐net arrays across Japan show that the largest shaking in northernJapan (near 2,000‐km epicentral distance) was caused by near‐causticSwaves, with triplication ofupgoing and downgoing waves from the deep source and reflected waves from the 660‐km discontinuity.Three‐dimensionalfinite difference method simulations confirm that the antiwaveguide effect of thehigh‐wave speed slab is to push the zone of larger intensity 300 km farther to south than might beexpected. TheSwavefront distorted by the slab has near‐critical incidence at the free surface producinglarge sP and generating shear‐coupled PL (s‐PL) waves with period >3 s. With increasing epicentraldistance theSincident angle exceeds critical, then total sS reflection creates large ground motion atlarge distance (>3,000 km) and even farther (>6,000 km) with sSS. The propagation of sS, sSS linking tosS‐PL, and sSS‐PL wave trains is very efficient in continental structures with thicker crust. The feltreports at large (4,000–8000 km) distances from the 2013 Sea of Okhotsk earthquake can be explained bylengthy, long‐period ground motion in the continental environment with amplification in sedimentarybasins and in tall buildings.This study was conducted with support from Grantsin‐ Aid from the Japan Society of Promotion Sciences (17 K01322)

Significant P wave conversions from upgoing S waves generated by very deep earthquakes around Japan

An important component of the seismic wavefield at moderate epicentral distances from deep earthquakes comes from seismic waves that are radiated upwards from the source. For very deep events, there is a range of distances at which upgoing S can convert into P waves that travel in the crust or in the upper mantle as the sPn phase. For a 600-km-deep event, sPn becomes a precursor to S from about 8°, and can have significant amplitude if the source radiation pattern is favourable. These conversions to crustal P have a very similar travel time property to S, and interfere strongly with S to produce complex wavetrains on both vertical and radial components. Where the locus of conversion falls on thicker continental crust, S waves can be coupled into partially trapped P waves in the crust that produce a long-period shear-coupled PL (s-PL) wave. Such longer period phases generated by large, very deep earthquakes can make a major contribution to sustaining large ground motion for considerable distances from the source. Observations of three very deep (> 575 km) events around Japan demonstrate the range of propagation effects associated with S to P wave (sP) conversion that plays an important role in shaping the later part of the recorded seismograms. The influence of sP conversion on the observed seismograms and the development of the s-PL wave depend on the variation of crustal thickness along the path and epicentral distance, and particularly on the locus of the conversion zone and the properties of the crust at that location.This study was conducted with support from Grants-in-Aid from the Japan Society for the Promotion of Science (No. 17 K01322)

Retrieval of Interstation Local Body Waves From Teleseismic Coda Correlations

We retrieve the local P wave empirical Green's functions between the elements of five different regional arrays across the globe by cross‐correlating and bin stacking the teleseismic earthquake coda waves recorded at each array. The stack is made using the coda of P and S wave phases for events in the distance range from 40° to 50° from the center of the array. With a sequence of time windows along the coda the various body wave arrivals can be tracked, using record sections constructed by binning the stacked interstation correlograms in less than 1‐km distance increments. The correlation of the coda part of each principal seismic phase produces highly coherent interstation arrivals for different analysis windows. Such arrivals can be reproduced by just stacking 100 arrivals from a pool of more than a thousand events, showing the stability of the observed Green's functions. Modeling for the structure beneath the Warramunga array in the Northern Territory, Australia, demonstrates that these arrivals correspond to multiply reflected arrivals from layers at different depths. The recovery of high‐frequency interstation body waves from the teleseismic earthquake coda opens the prospect of conducting local high‐resolution seismic imaging with teleseismic energy

Maximum depth of magnetisation of Australia, its uncertainty, and implications for Curie depth

AbstractThe Curie depth is the depth at which the crust and uppermost mantle cease to be ferromagnetic or ferromagnetic, the main cause of crustal magnetism, due to the action of geothermal effects. One method to estimate the Curie depth for Australia is to map the base of magnetisation derived from observations of magnetic intensity. We have used a nonlinear direct sampling inverse technique to fully explore the parameter space of a fractal forward model of magnetisation. This produces an ensemble of models that allow us to produce maps of both the maximum depth of magnetisation and its uncertainty for Australia. The base of magnetisation varies significantly across the continent, between 10 and 70km depth, with an uncertainty of 7–10km. The variations in magnetisation depth conform with the boundaries of geological provinces due to their differing magnetic properties: In general, cratons and older provinces generally show a deeper base of magnetisation results and hence may be inferred to have deeper Curie depths, reflecting that these areas are on the whole cooler. We also find general agreement in our results with known geothermal anomalies