Question 8
Asia is traversed by complex tectonic plate movements which makes the risk of megathrust earthquakes high in Asia. One example is the magnitude 7.1 earthquake that happened in April 2023 in Sumatra, Indonesia. Its intensity ratings are plotted in Figure 8.1 near the epicenter. Its epicenter is denoted by a star.
(a) A megathrust earthquake occurs in a subduction zone, where one tectonic plate is pushed under another.
(i) Identify the type of tectonic plate boundary nearest to the epicenter. [0.5 mark]
(ii) Identify which layer of the Earth this plate movement occurs in. [0.5 mark]
(b) Table 8 lists observations during an earthquake according to the modified Mercalli scale. Place a check mark on observations made in the city of Padang during the April 2023 earthquake. [3 marks]
- [ ] parked cars rock
- [ ] dishes and windows broken
- [ ] buildings shifted off foundations
- [ ] monuments fall
- [ ] felt by Sumatrans who are sleeping
- [ ] some heavy furnitures moved
(c) A magnitude 7.1 megathrust earthquake can generate a tsunami.
(i) On Figure 8.2, draw arrow(s) from the origin to show the direction of energy causing a tsunami. [1 mark]
(ii) Compare the velocity (faster or slower) and height (higher or lower) of the tsunami as it gets shallower from point X to Y. [2 marks]
(a) A megathrust earthquake occurs in a subduction zone, where one tectonic plate is pushed under another.
(i) Identify the type of tectonic plate boundary nearest to the epicenter. [0.5 mark]
(ii) Identify which layer of the Earth this plate movement occurs in. [0.5 mark]
(b) Table 8 lists observations during an earthquake according to the modified Mercalli scale. Place a check mark on observations made in the city of Padang during the April 2023 earthquake. [3 marks]
- [ ] parked cars rock
- [ ] dishes and windows broken
- [ ] buildings shifted off foundations
- [ ] monuments fall
- [ ] felt by Sumatrans who are sleeping
- [ ] some heavy furnitures moved
(c) A magnitude 7.1 megathrust earthquake can generate a tsunami.
(i) On Figure 8.2, draw arrow(s) from the origin to show the direction of energy causing a tsunami. [1 mark]
(ii) Compare the velocity (faster or slower) and height (higher or lower) of the tsunami as it gets shallower from point X to Y. [2 marks]