Nagaon records a magnitude 4.5 quake at 04:23, with no damage entry

The National Center for Seismology recorded a magnitude 4.5 earthquake at 04:23:47 IST on Tuesday, with its epicentre in Nagaon district, Assam. The coordinates on the official event page are 26.428 north, 93.060 east. Depth is given as 33 kilometres. The page does not list deaths, injuries or damage.

A 4.5 at that depth is a felt event in the district and often in neighbouring districts, and it is below the range in which the centre's public bulletins usually carry a damage survey. No such survey had been posted on the event page by Tuesday afternoon. Local reports noted the shock because it arrived on a polling morning in the state. The seismology file itself is the time, the place and the magnitude.

Assam sits on the plate boundary that has produced the state's larger historical shocks, including events well above magnitude 8 in the instrumental and pre-instrumental record. A 4.5 does not revise that hazard. It is the ordinary output of a network that now publishes an origin within minutes. The NCS page for this event is the primary record: origin time to the second, latitude and longitude to three decimals, depth, magnitude.

The 33-kilometre depth is the figure that decides how the shock is felt. A shallow 4.5 under a town is a jolt. A 4.5 at 33 kilometres is a rumble over a wider area and a smaller chance of cracked walls. The centre's default depth assignment on some automatic solutions is 33 kilometres, so the figure should be read as the published solution, not yet as a refined crustal depth. The event status field on the page was blank in the public extract.

Nagaon is in central Assam, on the Brahmaputra plain, away from the steepest Himalayan front and inside the zone the centre monitors for aftershocks when a larger event occurs. No larger event was attached to this origin in the public list on Tuesday. A single 4.5 with no listed companion shock is how most days on this network look.

What the morning timing adds is administrative, not geological. Polling staff and voters were already moving when the origin time passed. A shock at 04:23 is early enough to be the first thing a household reports, and early enough that a district administration can check booths before polls open. No booth-level damage note had been issued through the seismology channel. The Lok Sabha byelection in the same district later closed at 76.16 percent, with counting on 9 October. The turnout bulletin did not list the quake as a disruption.

The checkable line is short, and it is enough. Magnitude 4.5, Nagaon, 04:23:47 IST, 26.428 N, 93.060 E, depth 33 kilometres, no casualty entry on the National Center for Seismology event page. Anything beyond that, a felt radius or a crack in a wall, is not in the file.

The National Center for Seismology is the agency that owns this origin. Its event page is the place a district collector and a news desk are meant to match. Latitude 26.428 and longitude 93.060 put the point inside Nagaon district on the centre's own label. A report that moves the epicentre to a neighbouring district is not using this file.

Magnitude 4.5 on the centre's scale is the figure to quote, not a converted value from another network, until a second agency publishes a revision. No such revision was attached to the event page in the public extract. Depth 33 kilometres stays with the same caveat. Automatic solutions in this region often start at that depth and are refined later. If a refined depth appears, the felt area changes with it.

Tuesday's shock is a small origin on a busy network. The reason to write it down is the precision of the file and the hour. 04:23:47 IST is early enough to be confused with a blast or a lorry, and specific enough to end that confusion. The centre has published the second. It has not published a damage line. Both facts belong in the same paragraph.