Sains Ma1aysiana 28: 59-68 (1999)                                                                                              Sains Bumi/

                                                                                                                                                                Earth Science

Application of Shallow Seismic Reflection

in Subsurface Geological Mapping

Umar Hamzah & Abdul Rahim Samsudin

Pusat Pengajian Sains Sekitaran & Sumber Alam

Fakulti Sains &Teknologi, 43600 UKM Bangi, Selangor D.E. Malaysia

ABSTRACT

Shallow seismic reflection is one of the surface geophysical techniques to investigate indirectly subsurface structures within depths of 200 meters. Structures such as faults, sedimentary features, hydrogeological aquifers, depth to bedrock and limestone sinkholes are always related to the geological mapping. This paper presents some of the shallow seismic reflection results in imaging subsurface structures at a few selected localities. The presence of a limestone sinkhole as small as 20 ´ 5 meters was imaged at the old limestone quarry in Batu Caves, Kuala Lumpur. Sedimentary struc­tures, aquifers and thickness of alluvium on granite bedrock were imaged from surveys at Pekan, Pahang and Bacok, Kelantan. Faults have also been detected using the same technique from a survey in Midland, England. Currently a minimum depth obtained is approximately 20 meters and the vertical resolution is approximately 5 meters.

ABSTRAK

Seismos pantulan cetek adalah satu daripada kaedah geofizik permukaan yang digunakan untuk mengkaji secara tidak langsung struktur bawah permukaan pada kedalaman sehingga 200 meter. Pemetaan geologi bawah permukaan selalunya melibatkan struktur-struktur geologi seperti sesar, gejala sedimen, akuifer hidrogeologi, kedalaman batuan dasar dan reronga batu kapur. Kertas ini membincangkan beberapa keputusan survei seismos pantulan cetek yang dilakukan untuk mengimej struktur bawah permukaan dibeberapa lokaliti terpilih. Kehadiran rerongga dalam batu kapur bersaiz sebesar 20 ´ 5 m telah berjaya dikesan dalam batu kapur di Batu Caves, Kuala Lumpur. Beberapa struktur sedimen, lapisan akuifer dan ketebalan aluvium yang menindih granit telah dapat diimejkan dengan survei seismos di kawasan Pekan, Pahang dan Bachok, Kelantan. Struktur sesar juga telah dapat dikesan di kawasan Midland, England dengan menggunakan kaedah yang sarna. Sehingga kini kaedah seismos pantulan cetek hanya dapat mengesan struktur pada kedalaman melebihi 20m dengan resolusi menegak disekitar 5m.

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