The color or shade of the compressive quadrants can be specified with the. The focal mechanism stress inversion program for the macintosh written by john gephart at the institute for the study of the continents instoc in ithaca, new york. If depth values for each earthquake are included, the focal symbol will also be placed at its appropriate location beneath the earths surface. Pdf rake is a program that is used to examine the stress regime in a region, using information from an earthquake database. Determination the focal mechanism determination the source process earthquake collection seismic waveform the determination method of focal mechanism using polarity of pwave fast. Fmc computes the different earthquake parameters that can be obtained from focal mechanism data, classifies the rupture type of each focal mechanism, performs a clustering analysis of the data if required by the user, outputs the parameters in different formats and generates a classification diagram from the input data. There are six optional fields that can be included in the point datas attribute table fig. Orientation of the nodal plane is given with three angles strike, dip, rake np1 150, 87, 1 according to. The software rake louvari and kiratzi 1997 was used to organize the database and perform the queries. Understanding focal mechanism solutions focal mechanism solutions are simply fault plane solutions for earthquakesmeaning that they tell us the orientation in 3d space of two potential fault planes that may have produced the seismic wave signal associated with the earthquake. It is a convenient device for displaying radiation patterns, since information recorded by seismometers distributed over the earths surface may be transferred back to the focal. Focal mechanism diagram we use a graphical procedure which enables us to represent the global distribution of polarity data and the two nodal planes on a.
The program requires as input a gis point dataset of earthquake locations containing strike, dip, and rake values for a nodal plane of each earthquake. Focal mechanism determination and identification of the fault. Fpfit software package reasenberg and oppenheimer, 1985. Here, focal mechanism is described using nodal planes. In the example below, the principal one is given as input and auxiliary one is computed automatically.
Option on stats button on table display window requires a harvard cmt project database file. Gifs for select segments included as optional download. The earthquake was felt by many people in northern thailand due to several shakings and the energy of the main shock dispersed to chiang mai city and far away to bangkok. Earthquake focal mechanism wolfram demonstrations project. Scale is the size for magnitude 5 in inch unless c, i, or p is appended. The rake angles indicated that the northern part of the pfz is characterized by leftlateral strikeslip and reverse faulting. Create and plot a ternary diagram using rake angle to distribute focal mechanisms on a ternary diagram. Methods generally used to select the fault plane of earthquakes by waveform analysis are based on the ob. Rake is a program for windows, written in visual basic 3, and has all the advantages of programs running under windows. Stressinverse is a matlab or python software package for an iterative. Graphics for spherical distributions and earthquake focal mechanisms. Hash is a fortran 77 code that computes doublecouple earthquake focal mechanisms from pwave first motion polarity observations, and optionally sp amplitude ratios.
The first tool is the method of evaluating the distribution of the focal mechanism orientations of groups of earthquakes and displays the data on the triangle diagram. Vincecronin adraftprimeronfocalmechanismsolutionsforgeologists preface inrecentyears,ihavedevotedanincreasingamountofmyseeminglydecreasingresearchtimetothestudyof. This symbol is the projection on a horizontal plane of the lower half of an imaginary, spherical shell focal sphere surrounding the earthquake source a. Stressinverse is a matlab or python software package for an iterative joint inversion for stress and fault orientations from focal mechanisms.
It is similar to scons and make, but it has a number of differences. Focal mechanisms given with partial data on both planes. Focal mechanism determination and identification of the fault plane of earthquakes using seismic recordings 1559 local gps data are available, the fault plane may be unde termined. You can define the strike, dip, and rake angle of a fault and choose. By default for each focal point, 3dfm will create a black and white sphere or beach ball that is oriented based on the strike, dip, and rake values.
Many algorithms and software have been developed to define source mechanism, one of them is waveform inversion using cut and paste cap method. Strike is always defined such that a fault dips to the right side of the trace when moving along the trace in the strike direction. Focal sphere 3d focal sphere for a seismic point source is a sphere centred on the source and having arbitrarily small radius. Frank scherbaum, nicolas kuehn, and bjorn zimmermann have written an interactive ap to make focal mechanism diagrams and computer the other nodal plane, given the strike, dip angle, and rake slip angle of one nodal plane. Matlab package for stress inversion from focal mechanisms. There is universally a paucity of rake data in the focal mechanism. This tool operates within the environmental systems research institute esri gis software arcscene 9. In the case of a faultrelated event it refers to the orientation of the fault plane that slipped and the slip vector and is also known as a faultplane solution. Data needed is earthquakes catalog point featureclass including attributes of lon, lat, m,strike, dip, rake, all in numerical value. Rfoc can be used for analysis of plane orientation, geologic structure, distribution of stress and strain analyses.
This difficult concept is carefully explained using strikeslip, normal, and thrust faults. Fmcearthquake focal mechanisms data management, cluster. The explanations there are quite good and quite precise. The new software presented here integrate three analysis tools combined together is called ternary focal mechanism tfmtools software tools.
Fpfit employs a grid search over all possible values of the strike, dip, and rake to identify the best. The parameter space for the strike, dip, and rake parameters of the focal mechanism is explored in a non linear way allowing the evaluation of the degree of uniqueness of the solution, which is quantified through a confidence index. Fmc computes the different earthquake parameters that can be obtained from focal mechanism data, classifies the rupture type of each focal mechanism, performs a clustering analysis of the data if required by the user, outputs the parameters in different formats and generates a. For definitions of the terms strike, dip, rake, plunge, foot wall, hanging wall, reverse fault, thrust fault, normal fault, strikeslip fault, and dipslip fault, see aki and richards 1980 chapter 4, page 106. Mar 06, 2017 focal mechanisms explained incorporated research institutions for seismology. Earthquake locations the systematic location of seismic events in a region can be used to identify causative seismic faults. You can define the strike dip and rake angle of a fault and choose between different types of projections and focal hemispheres this demonstration generates earthquake focal mechanism plots also called fault plane solution plots or simply beach balls. The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. The program requires as input a gis point dataset of earthquake locations containing strike, dip. Every project on github comes with a versioncontrolled wiki to give your documentation the high level of care it deserves. Usage plotternfoch, v, x 0, y 0, siz 1, fcols black, labs false, add false arguments h. Resulting gif image has transparent white color for dilatational quadrants. Sdstereo an additional option entitled 3dstereo is included in rake. This python script arctool plot earthquake focal mechanism beach balls as shapefile.
Given strikedip rake or a set of fault planes, focal planes, rfoc creates structures for manipulating and plotting earthquake focal mechanisms as individual plots or distributed spatially maps. Aug 24, 2012 focal mechanisms are released after an earthquake to show what type of earth movement produced the earthquake. The software is for free and it is an excel spreadsheet that can be used in both pc and macintosh platforms. Focal mechanisms enter strike, dip and slip and see the resulting focal mechanism. The high fitting between observed and synthetic waveforms shows that the iasp91 velocity model can be used for focal mechanism observations within the northern part of the pfz. Study on three independent parameters of focal mechanism solution. Fault strike is the direction of a line created by the intersection of a fault plane and a horizontal surface, 0 to 360, relative to north. Focal mechanisms are derived from a solution of the moment tensor for the earthquake, which itself is estimated by an analysis of observed seismic waveforms. A new method for determining firstmotion focal mechanisms. This should only be selected for a limited subset of the data because the full database might take too much time, and if you want to see spatial patterns you need a small area with consistent patterns. Pdf fmcearthquake focal mechanisms data management.
Source depth and moment magnitude mw are also recomputed. On world maps, seismicity tends to locate along linear belts which define more active deformation compared to more stable interiors. Dotproc geoscientific analysis software dotproc software is designed to help geoscientists in the analysis of twodimentional 2d spatial data sets in a highly visual manner. It allows the user to specify tasks and describe dependencies as well as to group tasks in a namespace. These are released after an earthquake to illustrate the type of faulting produced the earthquake. Rake is a program that is used to examine the stress regime in a region, using information from an earthquake database. Crosssections of these events are plotted utilizing rake software. They use information from seismograms to calculate the focal mechanism and typically display it on maps as a beach ball symbol. The matlab code needs just the matlab kernel and no toolboxes are required. A windows program to plot earthquake focal mechanisms. Abstract rake is a program that is used to examine the stress regime in a region, using information from an earthquake database. Software for three and four dimensional gis in the earth sciences. Mar 06, 2019 by default for each focal point, 3dfm will create a black and white sphere or beach ball that is oriented based on the strike, dip, and rake values.
Folding a highamplitude folding simulations program for dos written by kenneth cruikshank at portland state university in oregon journal of structural geology 15. Pages in category structural geology the following 186 pages are in this category, out of 186 total. They also tell us whether the responsible fault was normal. Focal mechanisms pacific northwest seismic network. The program requires as input a gis point dataset of earthquake locations containing strike, dip, and rake values for a nodal plane of each. Magnitude can be used to color rings around the fault planes and scale the. Hash is designed to produce stable highquality focal mechanisms, and tests the solution. According to the activity of earthquakes and volcanoes along the manila trench and its adjacent region, combined with analysis of focal mechanism solutions and geophysics data, the manila trench is still being downward subduction in the depth of 200 km.
Corresponding python code requires matplotlib, numpy, scipy and os modules. The focal mechanism can be derived from observing the pattern of first motions, that is, whether the first arriving p waves break up or down. A line is drawn where the fault plane intersects the shell. This option plots two nodal planes of each focal mechanism as great circles in the lower hemisphere of the focal sphere, presented in a 3d image. Software to download usgs earthquake hazard program.
Other information, such as depth and magnitude of the earthquake, may also be included in the dataset. The subroutines in fortran 77, which i did not write are compiled into a python module, libhashpy. Introduction studies of the seismotectonic environment of a region require close examination of the stress regime of the area. Fault hanging wall foot wall dip rake azimuth slip fault hanging wall foot wall dip rake azimuth slip. Msatsi is a matlab software package that allows performing the stress. Depending on the distribution and quality of firstmotion data, more than one focal mechanism solution may fit the data equally well. Image surround the hypocenter with small sphere focal sphere, and project polarity. The focal mechanism of an earthquake is represented by a beachball diagram. Nov 19, 2018 the new software presented here integrate three analysis tools combined together is called ternary focal mechanism tfmtools software tools. Some sources of focal mechanism data in progress a focal mechanism plottercalculator. Louvari and kiratzi, 1997 with the variation of hypocenters, depth view of focal mechanism solutions, plots of the primary. Fmcearthquake focal mechanisms data management, cluster and.
You can define the strike, dip, and rake angle of a fault and choose between different types of projections and focal hemispheres. We created a new tool, 3d focal mechanisms 3dfm, for viewing earthquake focal mechanism symbols three dimensionally. Rake is a software task management and build automation tool. Figure 7 shows an example of the orientation of the earthquake nodal planes from earthquake focal mechanisms 857 this data set. Interpreting focal mechanism diagrams rake the direction of fault movement measured counterclockwise from strike and slip direction of hangingwall from 180 to.
These are typically shown using a socalled beachball diagram. It is noticeable the uniform organization of focal mechanisms in very wide regions, with few. Using visual studio dot net 2012 to create a windows based software tools for focal mechanism datasets analysis using. Focal mechanism solutions and its tectonic significance in. Focal mechanisms are released after an earthquake to show what type of earth movement produced the earthquake. The rake of the hangingwall slip vector is measured in the plane of the fault, relative to the.
903 426 292 1370 907 1502 593 297 881 1598 707 1554 421 1173 509 933 130 416 173 12 844 678 1286 244 829 435 481 312 664 1003