Gunawan Ibrahim

Characterization of tsunamigenic earthquake in Java region based on seismic wave calculation

This study is to characterize the source mechanism of tsunamigenic earthquake based on seismic wave calculation. The source parameter used are the ratio (Θ) between the radiated seismic energy (E) and seismic moment (Mo), moment magnitude (MW), rupture duration (To) and focal mechanism. These determine the types of tsunamigenic earthquake and tsunami earthquake. We calculate the formula using the teleseismic wave signal processing with the initial phase of P wave with bandpass filter 0.001 Hz to 5 Hz. The amount of station is 84 broadband seismometer with far distance of 30° to 90°. The 2 June 1994 Banyuwangi earthquake with MW=7.8 and the 17 July 2006 Pangandaran earthquake with MW=7.7 include the criteria as a tsunami earthquake which distributed about ratio Θ=−6.1, long rupture duration To>100 s and high tsunami H>7 m. The 2 September 2009 Tasikmalaya earthquake with MW=7.2, Θ=−5.1 and To=27 s which characterized as a small tsunamigenic earthquake.

Ratio of radiated seismic energy and moment to determine source mechanism of the 2010 Mentawai tsunami earthquake

The 25 October 2010 Mentawai earthquake has magnitude Mw 7.7 and shallow depth (12 km). Although the local people of Sikakap - the closed island near epicenter (78.33 km) only felt low shaking (II-III Mercally Intensity), it rised tsunami 7.4 m height causing casualties 447 people died. We suggested the phenomenon is the tsunami earthquake. Therefore we calculate the source mechanism by using W-phase method to determine its parameter. The result yield good value due to reference of GCMT solution with strike 340.3°, dip 8.3°, and slip 116.9°. The cross section diagram of hypocenter show the event located on the beginning of subduction. We obtain the values of seismic radiated energy 1.76×1014 Nm, seismic moment 5.37×1027 Nm, and its ratio is Θ = −6.1. It counted as the threshold of tsunami earthquake. The rupture process has long duration 82 s. The facts proved that the 2010 Mentawai as a tsunami earthquake.

Development of earthquake early warning system using real time signal of broadband seismogram

Earthquake pose serious threat of live and properties for urban area near subduction zone offshore and active fault on land. Jakarta and Bandung is an example of big city that no system of Earthquake early warning (EEW) event very high urbanization, and has many important infra structure in the area. The capital city is potentially high risk ground shaking. EEW can be usefull tool for reducing earthquake hazard, if spatial relation between cities and earthquake source is favorable for such warning and their citizens are properly trained to response early warning message. An EEW and rapid response system can provide the critical information needed to minimized lost of live and property and direct rescue. Earthquake ground shaking with magnitude M>6.0 from zone of Megathrust, southern of West Java should potentially damage in the area of west java especially Bandung and Jakarta City. This research development of EEW parameter such as amplitude displacement (Pd), rapid magnitude determination (M) and Peak gr...