Cyflwyniad

Yn hwyr neithiwr, ychydig ar ôl i'r rhan fwyaf o bobl Aberystwyth fynd i gysgu, ysgubodd sŵn clep ddofn fel ton drwy'r dref. Crynodd ffenestri. Dychrynodd anifeiliaid anwes. Camodd ambell un o'r trigolion allan, gan ddisgwyl weld rhywbeth amlwg; ffrwydrad, tirlithriad, storm. Yn hytrach, roedd y strydoedd yn llonydd a'r awyr yn glir.

Doedd dim byd i'w weld. Ni chlywyd dim byd wedyn.

Ond roedd pob un o'r tair gorsaf seismoleg o amgylch yr ardal wedi cofnodi'r un curiad o egni.

Roedd beth bynnag a achosodd y glec yn ddigon cryf i deithio trwy'r ddaear a chyrraedd pob gorsaf.

Ar hyn o bryd, mae ei ffynhonnell yn dal i fod anhysbys.

Eich tasg chi yw defnyddio data'r gorsafoedd i ddod o hyd i leoliad y digwyddiad er mwyn i'r awdurdodau wybod ble i ddechrau chwilio.

Gan ddefnyddio graddfeydd, cyfesurynnau a thriongliant, a allwch chi arwain ein chwilwyr i'r lleoliad cywir?

Cliciwch y botwm 'nesaf' isod i ddechrau.

Y Data

Rydych wedi derbyn map o Aberystwyth sydd wedi'i dynnu ar frys gyda grid troshaenu. Mae pob sgwâr o'r grid yn cynrychioli pa mor bell y bydd ton seismig gynradd (ton-P) yn teithio trwy'r ardal mewn un eiliad.

Fersiwn Pdf i'w argraffu.

Rydych hefyd wedi cael y data canlynol am leoliadau'r gorsafoedd seismoleg a'r amser y cymerodd i'r don gyrraedd pob un ohonynt.

Gorsaf	Cyfeirnod Grid	Amser cyrraedd tonnau-P (eiliadau)
Gorsaf yr Afon (A)	F1	6
Gorsaf y Bryn (B)	C7	2
Gorsaf y Cae (C)	I6	4.5

Mae gennych ddigon o wybodaeth nawr i gyfeirio'r timau chwilio i ardal addas - a allwch chi ddarganfod sut?

Cliciwch y botwm 'nesaf' isod i gael canllawiau ychwanegol ac ystyriaethau pellach.

Canllawiau

Mae'r her hon yn cyfuno gwybodaeth am gyfesurynnau grid â chyfrifiadau radiws i driongli safle.

Triongliant yw lleoli gwrthrych â 3 phwynt neu fwy. Po fwyaf o bwyntiau cyfeirio sydd, y lleiaf yw'r ardal darged

Rydym yn gwybod bod pob sgwâr grid yn cynrychioli pa mor bell gall ton-P deithio mewn un eiliad. Felly, os yw hi'n cymryd 3 eiliad i'r don-P gael ei chofrestru yng Ngorsaf yr Afon, gallwn dynnu cylch gyda radiws 3 sgwâr grid a gwybod bod y trawiad wedi digwydd o fewn y cylch hwnnw. Ychwanegwch ail gylch sy'n gorgyffwrdd â hwnnw gan ddefnyddio darlleniadau gorsaf arall ac fe gewch ardal lai. Ychwanegwch drydydd cylch ac mae'r ardal yn lleihau eto.

Mewn sefyllfaoedd yn y byd go iawn, anaml y byddwch yn gweld yn union bwynt 'ble mae'r holl gylchoedd' yn cwrdd â'i gilydd - ond, yn hytrach ardal gorgyffyrddiad.

Cliciwch y botwm 'nesaf' isod am ystyriaethau ychwanegol.

Casgliadau

Ar ôl i chi ddod o hyd i'r tair gorsaf ar y map a llunio eu cylchoedd perthnasol, efallai y byddwch eisiau ystyried y canlynol:

• Ble ddylech chi anfon y tim chwilio?

• Pam nad ydy'r cylchoedd yn cwrdd â'i gilydd yn berffaith?

• Pa fath o bethau a allai achosi'r math hwn o ddigwyddiad?

Gobeithio eich bod chi wedi mwynhau'r gweithgaredd hwn!

Introduction

Late last night, just after most of Aberystwyth had settled into sleep, a single deep thump rolled through the town. Windows rattled. Pets startled. A few residents stepped outside, expecting to see something obvious; an explosion, a landslide, a storm front. Instead, the streets were still and the sky was clear.

Nothing was visible. Nothing was heard afterwards.

But three seismology stations around the area all recorded the same sudden pulse of energy.

Whatever caused the thump was strong enough to travel through the ground and reach every station.

Its source is still unknown at this time.

Your task is to use the data from the stations to work out where the event happened so authorities know where to begin their search.

Using scales, co-ordinates and triangulation, can you guide our searchers to the correct location?

Click on the 'next' button below to get started.

The Data

You have been provided with a hastily drawn map of the Aberystwyth area with an overlaying grid. Each grid square represents how far a primary seismic wave (P-wave) will travel through the region in one second.

Pdf version for printing

You have also been provided with the following data about seismology station locations and the time it took for the wave to reach each of them.

Station	Grid Reference	P-wave arrival time (s)
Afon Station (A)	F1	6
Bryn Station (B)	C7	2
Cae Station (C)	I6	4.5

You now have enough information to direct the search teams to a suitable area - can you figure out how?

Click on the 'next' button below for additional guidance and further considerations.

Guidance

This challenge is combining grid co-ordinate knowledge with radius calculations to triangulate a site.

Triangulation is the locating of an object from 3 or more points. The more points of reference the smaller the target area.

We know that each grid square represents how far a P-wave can travel in one second. So if it takes 3 seconds to register a P-wave at Afon Station, we can draw a circle with a radius of 3 grid squares and know that the impact occurred within that circle. Add a second overlapping circle from readings at another station and you get a smaller area, add a third and the area becomes smaller again.

In real world scenarios, you will very rarely see an exact 'where all the circles' meet point - but an overlapping area.

Click on the 'next' button below for some additional considerations.

Conclusions

Once you've located all three stations on the map and drawn their relevant circles you may want to consider the following:

• Where should you send the search team?

• Why don't the circles meet perfectly?

• What kind of things could cause this sort of event?

We hope you've enjoyed this activity!