The great earthquake that occurred in Sagami Bay in Japan and killed about two and a half lakh (250,000) people is an example of which one of the following types of earthquakes?

Introduction / Context:
Japan is one of the world most seismically active countries, located where several major tectonic plates converge. Historical earthquakes in and around Sagami Bay, such as the great Kanto earthquake, have caused severe damage and large loss of life. This question asks you to identify the general type of earthquake represented by such a catastrophic event, focusing on the basic classification used in physical geography.

Given Data / Assumptions:

• The earthquake occurred in Sagami Bay in Japan.
• It killed about two and a half lakh people, indicating a very powerful event.
• Options include tectonic, plutonic, man induced, and isostatic earthquakes.
• We assume knowledge that Japan lies in an active tectonic zone with subduction boundaries.

Concept / Approach:
Most large and destructive earthquakes in Japan occur along plate boundaries where one plate is subducted beneath another. Such earthquakes are caused by sudden release of strain along faults due to plate movement and are classified as tectonic earthquakes. Plutonic and isostatic terms relate more to slow crustal adjustments or deep intrusions, while man induced earthquakes are triggered by human activities such as reservoir filling or mining. A huge natural earthquake in Sagami Bay is therefore best described as tectonic in origin.

Step-by-Step Solution:
Step 1: Recognise that Sagami Bay is part of a plate boundary region near Honshu, where the Philippine Sea Plate and other plates interact with the Eurasian and Pacific Plates. Step 2: Recall that major Japanese earthquakes result from sudden movement along faults associated with this plate convergence, which is the essence of tectonic activity. Step 3: Understand that man induced earthquakes are usually relatively small events linked to activities such as fluid injection, mining, or reservoir induced stress changes, not massive disasters killing hundreds of thousands. Step 4: Plutonic processes involve slow cooling of magma deep in the crust, and isostatic adjustment refers to gradual vertical movements due to loading and unloading, both of which are not typical labels for sudden catastrophic earthquakes. Step 5: Therefore, the large destructive Sagami Bay earthquake is classified as a tectonic earthquake.

Verification / Alternative check:
The great Kanto earthquake of 1923, associated with the Sagami trough near Sagami Bay, is widely described in seismology literature as a shallow crustal tectonic earthquake linked to the plate interface between the Philippine Sea Plate and the overriding plate. No credible source classifies it as man induced, plutonic, or purely isostatic. This supports the standard classification of such events in Japan as tectonic earthquakes.

Why Other Options Are Wrong:

• Plutonic earthquake: Plutonic refers to deep seated intrusive igneous processes, not a commonly used separate earthquake category for large shallow plate boundary events.
• Man induced earthquake: These are typically smaller, artificially triggered tremors associated with human activities; the huge Sagami Bay event was naturally caused by plate motion.
• Isostatic earthquake: Isostatic adjustment involves very slow crustal uplift or subsidence, not sudden massive fault rupture and widespread destruction.

Common Pitfalls:
Some learners become confused by the many terms related to crustal movement and may overthink the classification. A simple rule is that most large, naturally occurring earthquakes at plate boundaries, especially around the Pacific Ring of Fire, are tectonic. Reserve the phrase man induced for small, human triggered events, and use isostatic mainly for gradual vertical adjustment, not for catastrophic quakes. This approach helps in choosing tectonic as the correct category for the Sagami Bay earthquake.

Final Answer:
The Sagami Bay earthquake in Japan is an example of a tectonic earthquake.