The applet shows the ray paths and traveltimes for some bodywave phases, calculated for a Jeffreys-Bullen earth model and a surface focus.
Ray paths are constructed using traveltimes and their derivatives with respect to epicentral distance, calculated with a FORTRAN package of Ray Buland and Bob Engdahl ( from Software archive of the Seismological Central Observatory SZGRF, or mail to Klaus Stammler SZGRF ).

Two separate frames show

( 1 ) A cross section of the earth model, the Jeffreys-Bullen velocity-depth functions and/or a list of phases for which ray paths are drawn ( depending on the dimensions and the aspect of the model window ).
Rays are plotted from the focus ( SRC, top of the cross section ) to max. 72 stations at fixed epicentral distances 0 ... +180 [deg] ( distance increment 2.5 [deg] ).

( 2 )The traveltime curves for the phases implemented and for the Love and Rayleigh waves ( LQ and LR ).

To Stations | Phases | Ray colors | Examples | Download

START

calculates the coordinates and corresponding intermediate traveltimes along all ( 1564 ) rays implemented, using a table of traveltimes and derivatives and a velocity-depth table.
Label and function of the button change to RESET ( see blow ), dialog elements referring to the ray display are enabled.

HOW TO :

INFO displays to the actual cursor position.

in the model window ( RAYS ) :

depth ( DEPTH [km] ) and corresponding velocities ( P/S VEL [km/s] ) in cross section or velocity-depth display,

epicentral distance ( DELTA [deg] ), phases and traveltimes ( [sec] ) for the station, the mouse cursor points to on the periphery of cross section.

in the traveltime window :

epicentral distance ( DELTA [deg] ) and time ( TIME [sec] ) of actual cursor position,

epicentral distance ( DELTA [deg] ) and origin time ( T-ORG [sec] ) of a seismic trace, displayed in the traveltime window,

phase codes and traveltimes ( [sec] ) of selected phases for the epicentral distance of a seismic trace, displayed in the traveltime window.

HELP displays possible mouse button actions.

in the model window ( RAYS ) :

SET / CLR STATION selects one or a group of stations for which rays are to be plotted.

in the traveltime window :

SET / RES ZOOM WIND sets / resets a zoom window,

DRAG TRACE moves a seismic trace, displayed in the traveltime window,

DISP ACT / ALL RAYS displays ray paths of selected / all phases for the epicentral distance of a seismic trace, displayed in the traveltime window,

INC / DEC AMP SCAL multplies / divides by 2 the amlitude scaling of a seismic trace, displayed in the traveltime window.

WAVE FRONTS / RAYS 0 ... +180 / STEP xxx

selects the display mode ( model window ) :

WAVE FRONTS

plots only the endpoints of rays, forming 'wave fronts' for adjacent rays of the same phase.

RAYS 0 ... +180

plots ray paths from the focus to stations on the righthand periphery of the model.

Both display modes apply to selected phases and stations and enable 'snapshots' in descrete time steps :

RUN / HALT

starts / stops the continuous display.

STEP

increments the traveltime by one time step.

DEL_T 2 [sec] / 10 [sec] / 1 [min]

selects time increment.

RESET ( labeled START when loading )

resets the display to time = 0. for WAVE FRONTS, to time >= max. traveltime for RAYS 0 ... +180.

STEP xxx

displays one ray of a group of phases :

INC / DEC

increments / decrements the angle of emmergence.

REST

restors initial conditions ( angle = 0 [deg] ).

STEP DIRECT P / S

selects phases traveling directly ( without reflexion ) from focus to station, i.e. P, Pdiff and PKP / S, Sdiff and SKS.

STEP PKKP / SKKS RAYS

selects phases reflected at the inner surface of the core-mantel boundary.

STEP P'P' / S'S' RAYS

selects phases traversing the core twice ( reflected at the earth's surface ).

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Display modes WAVE FRONTS and RAYS 0 ... +180 :

The dialog field STATIONS selects / clears all stations
( SEL ALL / CLR ALL ).

Single stations or groups of stations are selected / cleared with the mouse in the model display.

Color code :
gray = station not selected,
cyan = station selected,
blue = station selected and hit by at least one of the phases selected.

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The dialog field PHASES allows to enable groups of phases and to select phases for the ray path / 'wave front' display.

Phase Codes :

P / S

denotes compressional / shear waves for ray paths in the mantel
( M in velocity-depth display ).

K

denotes phases traversing the core
( O.C. and I.C. in velocity-depth display ).

The first letter ( P / S )

denotes the wave type emerging from the source
( SRC in cross section ).

The last letter ( P / S )

denotes the wave type arriving at a station.

.c.

denotes reflexions at the mantel-core boundary.

.KiK.

denotes reflexions at the inner core.

.diff

denotes diffractions at the core-mantel boundary.

P'P' and S'S'

denotes phases traversing the core twice ( reflected at the earth's surface ).

SEL ALL / CLR ALL

selects / clears all phases of the phase group selected.

ALL PHASES / P PHASES / ...

enables all phases or a subset of phases for selection.

ALL PHASES

enables all phases implemented.

P PHSAES

enables compressional waves ( at source and station, P, PcP, ... P'P' ).

S PHSAES

enables shear waves ( at source and station, S, ScS, ... S'S' ).

PS PHSAES / SP PHASES

enables compressional waves at source, shear waves at station, resp. vice versa ( PS ... PKKS, resp. SP ... SKKP ).

P SOURCE / S SOURCE

enables all phases, emerging as compressional / shear waves at source ( P ... P'P' and PS ... PKKS / S ... S'S' and SP ... SKKP ).

STATION P / STATION S

enables all phases, arriving as compressional / shear waves at station ( P ... P'P' and SP ... SKKP / S ... S'S' and PS ... PKKS ).

SHOW CORE RAYS :

applies to phases traversing the core ( PKP, PKKP, P'P', SKS, etc. ).

I.C.

selects rays, traversing the inner core,

O.C.bc and O.C.ab

select the rays, traversing the outer core only.

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The color code of the ray display corresponds to the colors in the dialog field PHASES and depends on the phase groups enabled :

If more than one phase group is enabled
( ALL, P+S, PS+SP, P/S SOURCE and STATION P/S ) :

red = P-phases,
blue = S-phases,
cyan = PS-phases,
magenta = SP-phases.

If one phase group only is enabled :

blue-green = reflexions at the inner core ( PKiKP, etc. ),
magenta = core phases ( PKP, etc in the dialog field ) and rays traversing the inner core,
cyan and green = rays traversing the outer core only.

If display mode WAVE FRONTS is selected :

red = 'fronts' traveling with P-velocity,
blue = 'fronts' traveling with S-velocity,

The dialog field DISP allows to display / hide

the model+ray frame ( RAYS ) and/or the traveltime curves ( TRAVEL TIMES ).

NO TRACE / T E S T / TURKEY / SAKHALIN / MEXICO

selects a seimic trace for display in the traveltime window.

Traces are displayed in a time scale corresponding to the time axes of the traveltime display, and an adjustable amplification ( field TRACE SCAL., above the the trace ).

Epicentral distance and origin time of the event can be estimated by shifting the trace display horizontally and vertically to fit onsets to the traveltime curves.

If INFO is activated, some relevant parameters of a seismic trace can be displayed ( field INF, below the trace display ).

T E S T

simulates a seismic trace, showing the theoretical arriveltimes of the phases P, PP and S for an epicentral distance of 80 [Deg].

TURKEY ...

selects one of three traces, recorded at the station CLZ for earthquakes with different epicentral distances ( and azimuths ).

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EXAMPLES :

Rays ( RAYS 0 ... +180 )
STATIONS : SEL ALL
PHASES : only P PHASES enabled, P, Pdiff, PKP(I.C., O.C.bc and O.C.ab ) selected

Snapshot 14 [min] 0 [sec]
( parameters as above )

Snapshot 14 [min] 0 [sec] ( WAVE FRONTS )
STATIONS : SEL ALL
PHASES : ALL PHASES, SEL ALL

Traveltime curves and seismic trace TURKEY

Traveltime curves and seismic trace TURKEY
( Zoom + amplitudes x 4 )

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Download :

Class and html files for a local installation of the applet are available as a zip file and as a tar.gz file.

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